Just a few blocks from the beach, and one block from the Third Street Promenade is Hennessey + Ingalls art and architecture bookstore. H+I is not only the best specialty art bookstore I've ever seen (far better than any museum bookstore, and about 50 times better than Blackwells Art Bookshop in Oxford), it is the bookstore that is most fun to browse, without qualification. I would make an effort to come here every time I go to Los Angeles just to flip through their copy of Candida Höfer's Libraries.
As important as the enormous range of art books they have to the pleasant browsing experience is H+I's knowledgeable staff. When I asked if they had a copy of Every Building on the Sunset Strip, the guy behind the counter pointed out that not only did they not have it, but that a copy would cost me several thousand dollars. Obviously that wasn't what I was looking for, though he said they used to "always have a copy in stock". I was actually looking for Ruscha's Then and Now, but couldn't remember the title. He quickly identified what I was after and opened up a sealed copy for me to browse.