My shelves are grouped by technique. Traditional, baby, PPing, contemporary, educational., etc.
I like to pick up Q books at yard sales and 2nd hand shops. I once found one with many notations in it about the quilts made from the patterns and it is my favioite book just because of this passing on of information. So I now also love to write in my quilting books, listing what patterns, dates and info on instructions or how I changed it up a bit. In my way, I leave my little impression for the future.
peace