To set up 2,000 + items on pay pal is a mind blowing task.
Why not program your own cart, and just have pay pal process the final amount (see pay pal manual)
Does your client already have the details of the books on computer? If so a text dump into mysql is easy. Dynamic pages in PHP, simple cart and check out.
Two days work max. 1,000 pounds. I wish I could find clients like that!