Out of the numerous bookstores that I've been to, there are three that I adore, or I should say two that I adore and once I used to adore.
Waterstones in both London and in Birmingham England is amazing. It's the biggest bookstores, from what I understand, - though correct me if i'm wrong - in Europe. However, Powell's, the largest bookstore in the US, in Portland Oregon is even better, just because I'm a sucker for used and rare books. That said, I can go back to them for days on end. If I could take a sleeping bag in there to sleep, particularly in Powell's, I would. The other bookstore I was fond of was Sam Weller's books in Salt Lake City, Utah. It was an amazing little downtown bookstore that also carried obscure and rare books. Sadly, when they moved to a smaller building they had to get rid of a lot of their inventory. Thus the store lost a lot of what made it special.