I have so many good spells as a Priest and not enough bars to show them! Or is there a way to cast spell directly from the book? I can't figure one out.

It seems like if you can't do that, then spellcasting really should be limited to 2~ schools max or you won't have room to even use all the spells you could be! That seems like a really poor design decision, limiting player builds by the UI itself, which is otherwise beautiful to look at. This is especially annoying on my Priest since they get to start with 3 free spell books.