The game Dragon Age (Origins).

I sometimes came across books with specializations; I definitely remember there was a book for the Ranger and Paladin. After reading these books, the character would become a Ranger or Paladin, respectively. Maybe there are other options available for sale.

Actually, you should be more specific, and here's why: I myself played as a Mage throughout the entire game, hoping to find a book or have companions teach me. But! It turned out that to gain specializations (except, perhaps, for the Werewolf), Mages have their own, special path. So, tell me what class you're playing and what specialization you want to get :)

Diablo is an Action-RPG where the main task is to "hack and slash." However, that's not necessarily a bad thing. I myself have played Diablo II more than twenty times, at least.