anything by escher to be fair when looking at books to that intent to teach you something there isnt really any for me. I tried some anatomy books but i guess truth is i don't care for anatomy and realism. Also not a book but a magazine wich is free if u can get ur hands on it, are the issues from montana paint, recently picked up Tramontano and some other one but they are really good (interesting reads , plus i like a good magazine since they are pretty much extinct. Really there's lot of stuff that can do it as long as its not something that tells me what to do literally.