The Chronicles of Narnia and half a dozen other C.S. Lewis titles, but one of my favorites is his lesser known An Experiment in Criticism (which I reviewed in 2009). On Stories is a book of essays that continues with the same theme of literary taste, what it means and how it is formed.
I thoroughly enjoyed Lewis' thoughts on fairy tales, Tolkien, Dorothy Sayers and children's lit because those are subjects dear to my heart. (This is the book with the famous quote, "A children's story which is enjoyed only by children is a bad children's story.") He makes a valiant effort to define good art vs. bad art in his essay, "Different Tastes in Literature." The other essays (on authors and topics that were unknown to me) required perseverance. This is a perfect book for reading in short spurts, giving yourself time to mull over and digest its ideas.
Lewis had a wide range of reading tastes and mentions many authors who were popular during his lifetime but who have since dropped off the scene. The third essay was a tribute to new-to-me author E.R. Eddison. The day after I read that chapter, I saw Eddison listed on Nick Senger's list of 50 classics. (It's #22 - The Worm Ouroboros.) I love making reading connections!
Other authors mentioned by Lewis that sent me scurrying for more information were Tobias Smollet, Mervyn Weakes, John Collier and Alfred Mee. Lewis compliments Henry Rider Haggard for the first lines of the book She and H.G. Wells for When The Sleeper Awakes. He has high praise for James Stephens' Deirdre (published in 1923) and calls David Lindsay's Voyage to Arcturus a "shattering, intolerable, and irresistible work." His referral to Edwin Abbott's Flatland and George William Russell's poetry also added to my "books to investigate" list. Lewis admits that some of these authors have more imagination than writing skill, but that their stories are compelling nonetheless. Happily, most are free for Kindle so it won't be an expensive to explore them.