The Asian History section alone has to be more than 100 shelf-meters. There's piles of books everywhere! In addition, they have a whole section on exploration with lots of titles about Asia. Many of the volumes are second hand or review copies and pricing is attractive. There is a rare books collection as well, if you're into that kind of thing.
Best thing is, you never know what you'll find. There are so many books about Asia for example, that you will likely make new discoveries, that you did not realize you absolutely needed. I regrettably had to leave early as it was close to closing time, but still came with with a bagful of books. Very happy with what I found. I'm currently reading Derek Waller's The Pundits: British Exploration of Tibet and Central Asia. A beautiful hard cover volume (originally a review copy).