Man, I remember reading 'Quiet' and feeling like Susan Cain gave me permission to be myself. She doesn't really give a standard reading list in the book, but her whole philosophy points you toward certain kinds of authors. She talks a lot about the power of solitude and deep focus, so naturally you'd look for writers who explore inner worlds with care. I always thought her work aligns with novelists who treat introspection not as a flaw but as the main event. Writers like Marilynne Robinson come to mind—'Gilead' is basically a quiet, deeply reflective letter from a father to his son, all about faith and the inner life. Or someone like Haruki Murakami, whose protagonists often embody a kind of thoughtful, observant solitude. Cain's emphasis on sensitivity makes me think of Virginia Woolf's stream-of-consciousness too, diving into the minutiae of a single day in 'Mrs. Dalloway'. It's less about a formal recommendation and more about following the trail her ideas lay down.
For nonfiction, she'd likely point you toward research on temperament, but for fiction, the authors that get praised in her circles are the ones who make the internal landscape feel vast and worthwhile. I'd throw in Pico Iyer's travel writing about stillness, or even the essays of Annie Dillard. The throughline is a reverence for the rich interiority that introverts often inhabit, celebrated rather than pathologized. Reading her work shifted my own book choices toward narratives that don't mistake loudness for depth.