I sometimes find it useful to re-read my beginners books from my older and more jaded perspective. :P Especially since I have some really rubbish books that I didn't know better about at the time! It can be quite useful as it can show you how far you have come and sometimes how crap those books were in the first place! However like you, I don't tend to buy any new ones anymore.

I am on the search for more advanced books too, although I find them to be more subject specific and often quite ceremonial.