Post books you read, because they were namechecked in other book

I picked up both The Recognitions and The Notebooks of Malte Laurids Brigge after reading Jonathan Franzen’s How to Be Alone. And I’m damn glad I did.
Also, I first read Kafka because of a quotation in the front of a Potok book, I forget which one, I don’t think it was The Chosen but it may have been.

As a kid I discovered E. Nesbit specifically because of the extremely overt references in Edward Eager's books, which would always have the group of plucky, magic-discovering kids hang out at the library reading Nesbit. The spotlight on The Enchanted Castle was especially helpful.

Thoreau's Walden because of Paul Auster's Ghosts.