andreasaspenberg2: it is obvious that some patch nerfed the drop rate on spell books on the early levels. the first time i played(back in 1997) i got book of town portal on level 2. here, i got it on level 3. i never even played the dungeon in tge patched version before i played the gog version. after patching i played multiplayer on battle.net only and only the last 4 floors. i never played single player in that version.
I know this post is old now so maybe you're not looking, but man, that's the nature of random. I've done playthroughs of this game where I got dope shit on the first couple floors, and playthroughs where I'm not finding much of anything.
Luckily, if you hate the world that generated, you can start a new game with your same character and it'll all be different. Maybe you'll get more lucky than before.