I always got my best book recommendations from my old library cart. Well, the library cart wasn't really mine. I was a shelver at my town's library, before I started college, and I would use their carts to do my job.
I first noticed something was up with the cart when I was shelving juvenile paperbacks. These were the lightest books we owned (and kept in the worst shape - kids are brats). But when I was rolling the cart, it was heavy. It groaned when I pushed it, and steering it was a mini-workout. It wasn't this hard to move a double-stack of adult non-fiction.
What was really odd, though, was as I removed more books, it barely got lighter. Finally, when all of the Fairy Princesses, Mary Kate and Ashley's, and other stupid books were shelved, its weight became normal. Only R.L. Stine's Goosebumps remained, and it was actually pretty light, even lighter than I'd expect.
I shrugged the incident off. But then I noticed it happening more and more. And then I noticed patterns