Kramer's is more than just a bookstore - it's a local hangout in DC that's near Dupont Circle. It's got a nice collection of books, is open late everyday and 24-hours on Friday and Saturday.
Kramer's is fairly small so it feels very quaint. The bookstore is kind of split into two sections just by the nature of the space it's in. Because it's small, the collection of books is a bit smaller, but it also allows you to peruse a lot more titles in a lot of sections you probably wouldn't look through.
In the back of Kramer's is Afterwords, their coffee house serving beer, wine, breakfast, brunch, dinner, and desserts. There's live music overlooking the bookstore on the second level Wed-Sat night and free internet at the bar.