Bishops do confuse me, because there is either too much choice or too much to cover, depending on the other classes in the party.
Just have your Bishop concentrate on whatever spell books aren't well covered by other party members.
Reading this thread really makes me want to play through Wiz 8 again. I'd like to give some of those hybrid classes a try. Unfortunately, the length of the game goes against it for me. It's just too damn long to fit into my gaming schedule again.