Porter Square Books is stuck in the middle of a bland strip mall, but it's a gem of an independently owned bookstore. The layout leaves a little to be desired, but they have a very good collection of books in all different genres.
Cafe Zing inside replaces any need to go next door to Dunkin Donuts or look for a Starbucks (is there one in Porter Square?). The coffee is all organic and packs an extra punch.