Looking for something to read on your travels? There are plenty of bookstores around Hoan Kiem Lake in Hanoi.
Just past Trang Tien Plaza, a shopping mall at the corner of the lake, you'll find a street with many different bookstores. This branch of Highland Coffee (where you can find amazing Vietnamese coffee for decent prices) is attached to a bookstore. Most of the books are in Vietnamese, but climb to the second floor for a selection of international books, many of which are in English. The store has a good collection of books about Vietnamese history and culture.
Just across the street, Kimmay is a really interesting store. Part clothing store and part bookshop, the store has a selection of art and fashion books in English.
If you are looking for some cheap used books, check out the booksellers along the road just around the corner. Although most of these books are in Vietnamese, you'll be able to find (photocopied) Lonely Planet guides and books about Vietnam (such as "The Quiet American").
Head to the other side of the lake for the best selection of English books all about travel, Vietnamese history and culture, and art. The store is also part souvenir shop.