I love books and Amazon used is one of the best sources for used reef books. I managed to buy a few books that I lost, one of which came from a library and I'm pretty sure it was read by no one. It was in pristine condition and I paid less than a 1/4 of what the original price was. I also think books are what's missing from new hobbyist's checklist when getting into the hobby. The root fundamentals are virtually unchanged and you could pick up a book from the 80's or 90's and set up a tank based on what's inside and be successful.