A list of four books per letter of the alphabet. Each set of four is arranged from most commonly shelved to least commonly shelved on Goodreads.
For the most part, books in the #1 spot have been shelved >2 million times, #2 spot 800k-1.4 million times, #3 spot 200k-500k times, and #4 spot <100k times. These numbers are lower for the letters Q, U, X, Y, and Z.
Hopefully the more "obscure" books can provide a challenge even for the very well-read, though I tried as much as possible to choose books that are somewhat well-known even if they are not as popular on Goodreads.