If you want the real detailed resources behind Heroes V, you don't need to go any further than to check out these impressive fan manuals. This is the site that created the manuals in the GOG release's FanDocuments folder, though you might want to go there yourself if you are looking for the manuals for the original game or Hammers of Fate, as their campaigns use slightly out-of-date rules for the sake of internal consistency (this also applies to HoF's multiplayer, which was simply never patched).

http://www.heroesofmightandmagic.com/heroes5/game_manuals.shtml

Also included in the GOG release is the Skill Wheel, which is a great way to check out builds ahead of time. If you're looking for the ones used by the Original game's campaign or Hammers of Fate, check the comments for the 1.1 release and the most recent 2 release, respectively.

http://www.celestialheavens.com/viewpage.php?id=520

These manuals are pretty good. It's silly not to get them!

Great manuals! Thank you!

The Tribes of the East version of that manual actually is included in the GOG release (it's located under Documents->Fan Documents in the HoMM5 start menu folder). The skill wheel is also included in the same location.

So they are! I will amend the post!