Blackwell's is on a Broad Street which has other booksellers, but now those book stores are mostly chains. There are also lots of tourist shops now... Blackwell's is right next to the new Bodleian.

Inside Blackwell's:
The shop is in an ancient building with various large and small rooms. On the bottom floor, you'll find philosophy, psychology and politics among other things (an appropriate location for these topics, isn't it?). On the entry floor, you'll find fiction and new releases. On the top floor, you'll find rooms with reference materials, foreign languages, linguistics, theology, etc. It's a treat to wind your way around the building.

Cattycorner from the main Blackwell's bookshop is their art store, where they sell prints and art books. I'm not sure it's still there, though. I heard rumors about it leaving.

Near both these stores (a 3 minute walk) is the oldest university library in England - the Old Bodleian. I once went into the stacks and pulled out several anatomy books from the 1600's. It was fascinating. The language was slightly different, along with the lettering ("f" was pronounced as "s"), but it was an entirely different weltanschauung. The book I read at length discussed how the genitals contained the "life heat" of the body. In other words, they believed the genitals generated bodily energy. This was obviously before the discovery of blood circulation. Fascinating...