Before books, students had to tote engraved granite slabs all over campus, which is why the most accomplished philosophers gave the best piggyback rides. Enjoy lighter reading material with today's Groupon: for $10, you get $25 worth of used books at PT Campbell BookDealer.

Lauded as one of five great London places to buy a used book by readers of the London Free Press, PT Campbell BookDealer invites readers to browse more than 35,000 used, antique, rare, and collectable books housed in a 150-year-old building. Customers wind through a labyrinth of shelves packed with a daily changing selection of classic literature, nonfiction tomes, and fiction books, each generally sold at half off cover price ($5–$10 on average), with some books priced higher based on factors such as the item's age, scarcity, and number of celebrity bite marks. Young readers can decipher the themes of children and young adult books (mostly under $5) while their parents practice turning the pages of antique and university publications ($10+), scan futuristic science fiction, or pick up tips from parenting guides that line oak showroom walls. PT's expert book buyers carefully inspect each item that is brought in, ensuring that all books are in good condition and free from defects such as water stains, missing pages, or spontaneously shouting out their twist endings.