The game Dragon Age (Origins).

After reading these books, the character would become a ranger or a paladin.

In my opinion, the hero simply gained the opportunity to upgrade a specific skill – they didn’t automatically receive it. :)

Like Diablo?

No. Diablo is an Action-RPG where the main task is to “hack and slash.” However, that’s not necessarily a bad thing. I personally played Diablo II more than twenty times, at least.

But is it actually a good game?

As I mentioned somewhere before, it’s a good game, but there’s nothing particularly special about it.