There's a list in the manual's appendix of how many Spellbooks you need for various effects. It tells you how much of a cast cost reduction X books gives you, as well as how many spells of each rarity your book will contain.
There is also a list of effects that can be enchanted to an item, and how many spellbooks in each realm of magic are needed for them. For instance, you need a fair number of Nature spellbooks to craft Regeneration magic items. (If you get a Regenerating Pathfinding hero with an entourage of sprites and, say, colossi... That's how we say gg, kids.)
Actually, if you can afford it, it's usually better to start out with a Granary. My starting build for a new village is typically Builder's Hall->Granary->Smithy->Marketplace->Farmer's Market; at the end of that you're getting a fair amount of population growth bonus and five food per turn. Housing is okay when you don't care as much, or when you can't afford to buy the builder's hall and granary, but getting at least to the granary is significantly better for fast growth of a village than early housing, I feel.
Designing your wizard can be tricky. Going multiple colors gives you massive flexibility and you can do a lot with early spells-splashing Chaos can get you Warp Wood and Eldritch Blade, a few Nature books can give a host of useful enhancements like Waterwalking, Pathfinding, plus the dreaded Web->Cracks Call combo (25% chance of killing anything in the game, regardless of magic resistance, defense, hits, or magic immunity).
Going a single color, though, is the only way to give yourself the major endgame power of the very rare spells. Check the appendix and see how many Very Rare spells you get; I think getting them all requires all but one pick in that realm of magic.
Going a single realm is hard, especially early game. You can't do much magic trading, because you're ahead of anyone else in your own realm and don't have any others. A lot of your spells are probably outside of your price range. But if you can survive to the endgame, Very Rare spells are, almost entirely, utter gamebreakers for all involved.
There's a few decent builds to try out.
The Crusader: 9 Life books plus the Warlord pick.
All your units will get a bonus level for free. Couple that with the Altar of Battle (all units produced in enchanted city are Elite), the Heroism spells (enchanted unit is Elite), and the Crusade spell (another bonus level; this plus Warlord, together, are the only way to get Champion-level units) will make your normal units borderline unstoppable... and the rest of Life's unit enchantments will take the "borderline" right out.
The Cult Lord: 9 Death books plus Infernal Power (or 4 Death books, Infernal Power, and 5 books in another color of your choice):
You need a race with the ability to build Cathedrals for this. Infernal Power will juice up your power production from religious buildings nicely, but it's the relationship with Dark Rituals (Death common) that really stands out. Throw Dark Rituals on a city once you get a Temple or Parthenon in place, and mana production will skyrocket; with a Cathedral in place, that city will produce a ridiculous amount of mana by itself. You can practically ignore nodes with this build, because even on the "Powerful" magic power setting a single Cathedral-equipped city is going to significantly outpower even Myrran nodes.
The Superhero: 11 Life books (This one's more just for fun and not particularly practical in the more difficult levels)
For your picks, make sure you draw Incarnation. (Having 11 books in one color of magic lets you pick 2 Uncommon and one Rare spell at the start of the game). Put all your production towards casting Incarnation; Torin the Chosen is an incredibly powerful Hero even without help, but throwing Heroism on him and feeding him all the enchantments you can muster will let him steamroll without much effort. If you get to the lategame, enchant him some gear, and he'll be eating Drakes and Wraiths for breakfast.
The Artificer: At least two picks in Nature, Chaos, and Sorcery, plus the Runemaster, Artificer, and (optionally) Alchemist picks. I personally put the rest into Nature to pick up Waterwalking and the ability to enchant Pathfinding, but it's really up to you. Rush Summon Hero or Summon Champion, make them some gear at a quarter of its actual cost, and set them loose. They'll be waterwalking across the map at warp speed with Pathfinding and some move speed bonuses from the artifacts, and will be able to solo against impressive odds.
Chaos Incarnate: 10 Chaos books. Ditch Chaos Mastery; it's not particularly worth it compared to what else you could be getting. Pick from these: Conjurer will make your summoned creatures very useful; Hellhounds will be dirt cheap, Fire Giants will make a good midlevel force, and Chimeras can solo almost anything but other Chaos creatures if you research Warp Reality and drop it on the battle. Channeler (does it require two picks? It's worth a Chaos book) is almost tailor-made for Chaos, because it relies so much on combat casting to be effective; it allows you to cast your fireballs without paying triple the mana cost from range penalties. Alchemist will be a big help in keeping your mana up, because Chaos is extremely mana-intensive.
Personally, I recommend Conjurer. You can rely on Hellhounds and Fire Giants to be a main force in the early game, and the cost reduction is extreme when coupled with the flat cost reduction you get for having so many Chaos books. The Giants can defend you all the way to Chimeras, and those are practically unstoppable once you have the mana to support them properly.
The Control Freak: Archmage or Conjurer plus the rest into Sorcery.
Archmage is a decent pick for Sorcerors because being able to rapidly cast gives you a big advantage. Sorcery gets probably the best in-combat summons in the game; Phantom Warriors are dirt cheap and the skill bonus for Archmage lets you summon them at an enormous rate, and Phantom Beasts will tear through even the most heavily-armored units like they're made of delicious pudding thanks to their Illusory attack (ignore all armor unless defender is Undead or Immune To Illusions). Spend the game using your spells to keep your opponents off balance; use Detect Magic to see what they're casting, then Spell Blast them just because you're bored.
[edit: Removed WALL OF TEXT and replaced with specific builds]

That's right - housing is a special setting, not a permanent addition to the city, isn't it? Now I remember.
It's probably a good idea to let the city build housing at least until you've picked up another population figure or two - enough so that you can allocate enough villagers to production to start building basic structures in a reasonable amount of time. Boosting your population early on pays off; otherwise, you may feel suffocated by not having enough production to get things moving.

Housing converts your production to population (can't remember the ratio) , so it's not all that useful if you don't have a decent amount of production. If you have the (iirc) 400 gold, it's far more useful to start a new city by paying for a Builder's Hall and a Granary than spending a couple of turns waiting for additional pop from Housing. A Granary improves your population growth while you're building other stuff, Housing only helps while you're using that setting.

Makes sense. I haven't played in a few years, so forgive my recollection. Come to think of it, I think I usually just went for the granary first, especially a bit later on when you can afford to just buy it outright.
I'm home for lunch now, so I'm looking up housing in my old Prima guide. Looks like the formula for the percentage housing bonus is workers divided by population, plus additional bonuses for the sawmill and builder's hall. If there is only one population point, however, the bonus is always +50%.
The population growth rate per turn is (maximum size - current size + 1) / 2, rounded up, then multiplied by ten. So, a city of one on a square that supports ten would grow by 50 people per turn. A granary adds 20 people per turn (actually a bit more, since it increases max population as well), a farmer's market adds 30.
Anyway, rule of thumb: if you can build something without going crazy waiting for it, you probably have enough workers. :p

Nope, not anything. ethereal units (phantom warriors, etc) are immune, IIRC. The Necromantic wraithform enchantment can grant that to any unit.
There are a lot of single-color strategies which actually make the game rather easy even without the Very Rare spells:
Sorcery gets you invisible flying warships.
Death lets you use the Wraith rush which can wipe out everyone very quickly.
Nature lets you make the slightly more expensive but also very effective Gorgon Rush.
Life has several options - Invulnerable Enduranced Guardian Spirit Rush (even faster than Wraiths strategy, but slightly more vulnerable), Incarnation which you mentioned (and which tends to die a lot on Impossible difficulty), or Stream of Life (with a few cities you'll soon have more gold and mana than you know what to do with.)
Chaos - well, that's a problem. The best I've come up with is hit-and-run tactics using gargoyles and Flame Strike.
I'd pick Life instead of Chaos. Heroism, Guardian Spirit, Healing...
Also Artificer+Runemaster lets you get more mana from Artifacts than they cost to enchant! (gamebreaking, really)

A lot of great stuff in this thread, it's definitely inspiring me to play more. Thanks guys.

If we add traits: Channeler + Conjurer + 8 Chaos Books = Hellhound/Fire Elemental spam.
You should have your race's good units along with a bunch of big Chaos damage spells once the rush turns ineffective.

I'm on my 4th completion run now, damn this game is addictive.
First tried at hard but failed, then at normal succeeded, then as a myrran full life at Hard won, then Hard myrran Troll full sorcery, highest score of 4500.
Then tried Impossible but made the error of engaging in combat too fast, should've first tackled all of the ruins and nodes for gear and maybe an extra spellbook or 2.
And now I'm trying a combination of 3 books, on hard and when thats done I think I've got the skills to succeed in Impossible.

How about Hellhound spam + Raise Volcano?
Anyway, try a no-book setup, it'll give you a very different game. You do have to pick Myrran, Warlord, Channeler and Famous to keep within the 6 trait limit, this lets you pick two of Alchemy, Artificer, Conjurer and Charismatic.

I think I tried something like that before, but could only succeed on Normal. The problem is that I actually suck at strategizing, so I usually go for the cheap superhero or superunit rush approaches :).
Another fun game I succeeded with on Normal (i think) is to only send recruited (i.e. not built or summoned) units out of cities, no heroes.

I was going to say "Runemaster requires 2 into Chaos/Nature/Sorcery", but I must have had a brain fart when I played that game because you're right, that's Node Mastery and it only requires 1 each. Life probably would have made that game easier!
Actually, I think I did wind up with 2 life books. Bleh, now I can't remember the build I used in that one game.

Here's a good site for MOM stuff....


http://www.dragonsword.com/magic.php .
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Had a small games business in the U.S. from 1991 to 1997, met and spoke to Alan (Emrich) many times during that period! He and Johnny Wilson ran the U.S. magazine Computer Gaming World; probably the best gaming magazine in the world in it's day!

Anything Alan put his hand to was as perfect as the Master of Magic strategy guide. He always went that little bit further and the MoM guide is probably the only guide that has so much stuff in it, it probably has stuff you don't need!