Books are nice. You don’t have enough books, so you should really get some more. Here are some suggestions on books about design.
Don’t Make Me Think by Steve Krug
First published in 2000, this is one of the best books written on understanding how users interact with websites.
Newspaper Designing by John E. Allen
Even though it was published in 1947, before there were any real schools of newspaper design, many of the concepts still hold true today. Perhaps more interesting, the author makes predictions for the newspaper of the year 2000, pretty much all of which have been spot on.