I've lived and worked in Hay-on-Wye, Town of Books, for about 15 years now, in various shops.
The best job ever was full time at the Children's Bookshop. As we only sold secondhand books, we had no contact whatsoever with publishers, but the variety of what we sold was so much greater than a new book shop, and it was possible to read and learn from some great authors. I discovered the delights of Antonia Forest there, who wrote school stories with linking family stories for the holidays - now very rare and collectable in the original, but being re-printed by Girls Gone By, the only new books we carried, as they were all reprints of rare and out of print books.
You do get to see what sells, and what sort of person buys. A lot of our books were bought by adults re-living their childhood, but it was also interesting to see what the kids went for, and how their choices were affected by what the adults remembered.
You also get to meet some interesting people, and talk to them about favourite books.
Also, I've always been able to take my dog to work with me. She had her own chair at the Children's bookshop, and biscuits at coffee break, and will go and say hello to children even when she isn't in the shop. When I worked across the alleyway from the pet shop, she used to lounge around outside going: "I'm cute, tickle my tummy - and you can buy a biscuit for me just over there." When I left that job, the pet shop owner laughingly threatened to sue me for loss of earnings!
One of the benefits of living in Hay, without actually working in any of the shops, is the Honesty Bookshop. This is where the surplus stock from Richard Booth's bookshop (the biggest and original bookshop in the town) goes to die. It's out of doors, in the Honesty Gardens, and the books stay out all summer, gradually getting mouldy in the rain. Get in while they're fresh, and you can come away with an armload of books at a time, on every concievable subject.