A large component of the game has always been wandering between Gitala village and Galatako to shop scum for spell books. The magic item merchant in Odrewold rarely has books. You also want to pick up good looking wands/scrolls as you can. You won’t be reliably casting a *ball spell for awhile yet, though (to wit, my best caster at level 6 can only cast them at 72% and now I’m often facing foes for which it is minor damage at power level 1). CC spells (sleep, confuse, stun, blind, etc) are much more valuable as a rule. That and the 3x3 “field” spells. Web is better than you might think. Create Water is great in battles with lots of melee action (it will take a loto f heat off your front line), and actually it’s not bad at pinning distant ranged groups either. Those are the best books to hone in on. And if you have a choice between e.g. cold ball or holding out for some CC, you probably want to do the latter.
There are several early(ish) game opportunities to pick up some nice platemail for the golems, which should help. Mine tend to be my sturdiest characters, so maybe you are getting a bit unlucky.