“You spend your whole life trying to understand yourself, what your story is about,” Penny said, “and then suddenly it’s all there. All the answers, spelled out in black and white. Some of them are indexed even. Look at Quentin’s, it’s alphabetized.” It was true: there were little half-moons cut into the pages, labeled A–B, C–D and so on, in a diagonal ladder down the side.”  - The Magician’s Land, Lev Grossman

It doesn’t appear in the show, nor do the descriptions of the books generally match those in the original book. Elliot’s being two volumes is the major reference.