I'd love to know some good book stores, too, seeing that I'm already living here! I haven't been here long, but here are some thoughts.
As far as restaurants go, there are many and good ones to choose from around M street and Dupont Circle. I'm a big fan of thai food, and I highly recommend Basil Thai on Wisconsin Ave., Thai Phoon in Dupont, and Bangkok Bistro in Georgetown.
For museums... all the smithsonian museums are free! There is also a free jazz concert in front of the National Gallery of Art every Thursday evening.