Selexyz Dominicanen Bookstore, Maastricht, Netherlands A different kind of place of worship, this bookstore has found it's home in a Dominican Gothic church from the 1200's. After the Napoleonic invasion, this church has housed a great deal of different things, from car shows to bicycles to boxing matches. After extensive renovations, the church was reopened as a bookstore in 2006. You can read more (and see more pictures, including the one above) here and read more here.
El Ateneo Bookstore, Buenos Aires, Argentina This theatre house was built in 1919 and called The Great Splendid. Now housing books instead of plays, this store holds a huge collection of books, with private boxes converted into reading rooms. While the English selection of books is minimal, this store is high on the WOW factor and certainly one of the most beautiful bookstores in the world. More information can be found here. Picture by CPX de Mex. You can also read about a theatre turned into bookstore in Toronto here.