The books I picked for this task:
* My hardcover boxed set of Thomas Mann's complete novels (7 books)
* My one-volume omnibus of The Collected Jack London,
* A three-novel book club P.D. James omnibus edition named Deadly Pleasures (and containing the novels The Black Tower, Death of an Expert Witness, and The Skull Beneath the Skin)
* ... and, of course, my Oxford Shakespeare Complete Works.
Altogether, they came to a weight of 8.5 kg (= 18.7 pounds).