Great selection of books and magazine with a big focus on rare. out-of-print books Japanese photography. Can sends hours in this little shop. I'd try to avoid on Market day (Saturday) if you want to have a good look as it can get a bit busy for such a small space.
Slightly biased as this is where I live, but Stoke Newington is great place to spend lazy saturday / sunday afternoons getting sloshed with friends. There are 10 + pubs within walking distance who all are great places for one reason or another. I'll pick out the White Hart for its huge beer garden...
One of my favourite things about London is the underground transport system itself. I love the design of the information systems and the stations have so much history — some of them dating right back to the 1800s.