The most popular book in my library is Harry Potter and the Sorcerer's Stone, which is in 37,389 libraries and is the most popular book on Library Thing. I have read it, and I enjoyed it very much (but I am not one of the 364 reviewers). It wasn't my favorite of the Harry Potter books- I think Prisoner of Azkaban will always be my favorite.
Of the top ten books on Library Thing, the only one I don't own is The Da Vinci Code.
What about you? Which are the most popular books in your library?