Librarista is a hip new Nimman spot that's a great place to while away a few lazy hours. It's not just a coffeeshop - the owner has built a library alongside of it that's filled with interesting coffee table and photo books that you could spend days looking at. Beanbags, low tables and a strict no-shoes rule add to the atmosphere. If it's not too hot out, there's also a lovely garden out front. The coffee is expensive at 70 thb and up, but the library books are worth it.
Unfortunately, Librarista isn't the best place to take your computer - you're limited to one hour of internet per drink, which isn't a big deal except for the fact that your connection cuts out and you've got to get up and get a new one every once in a while. Not exactly conducive to getting things done.