Along busy avenida de Santa Fe in Barrio Norte is a large, Indigo-Chapters type bookstore called El Ateneo Gran Splendid. This is a beautiful store.
Originally built as a theatre named Teatro Gran Splendid in 1919, the building was leased to a major business conglomerate in 2000. When renovations were completed it became the flagship store for El Ateneo.
The store now boasts over one million visitors each year, and it's easy to see why, at least from the beauty of the place. In 2008 The Guardian named it the second best bookstore in the world and that sealed its fate as a destination.
As for being a great bookstore I cannot say. While various guide books and travel videos on the web suggest a significant English language section of books, the reality is a selection of mass market titles that would make any bookseller from Canada cringe. The display of books is only just routine, though the setting cries out for slightly more somehow. On the selling floor there aren't all that many chairs for customers to relax and review their purchases, though there is a mediocre cafe on the former stage where you can relax with a cafe, or a glass of wine.
Customer service appears to be lacking, as seems the case throughout much of the retail trade in Buenos Aires. Store staff are often indifferent towards customers at best, and sometimes blissfully ignorant of them altogether. What a difference from another magnificent bookstore, Munro Books in Victoria, Canada, where the setting is great and the service is exceptional.
All that being said, El Ateneo Gran Splendid is worth the visit for the visual feast alone.