1) Cloudy With a Chance of Meatballs by Judi Barrett & Ron Barrett. Seriously. I write stories about giant beetles, implausibly huge trees, and uncannily massive playground equipment. I have no doubt that those resonate with me in part because of how much I liked this book as a child.
2) Lord of the Rings by JRR Tolkien. There's no denying how massively influential this was on me from the time I read it at age 12 through college (and beyond). Its direct influence on my writing is less than you might think, but its indirect influence is huge, both on my desire to write and on my imagination.
3) Language of the Night by Ursula K. LeGuin. A nonfiction book examining what fantasy and science fiction are and how they work. Not exactly what you'd think would grab a 16-year-old. Especially since at the time I read this, I'd read one of her novels and hated it (to my embarrassment today, since I've loved most everything else she's written), but as this was a paperback about fantasy and SF, the small-town librarians shelved it with the other fantasy/SF paperbacks, and I grabbed it. And it forever changed how I looked at imaginative fiction.
4) The Book of Atrix Wolfe by Patricia McKillip. It's hard to even single this one out, as I actually don't remember a lot of details of the story. But...I found this on a bargain books table and bought it for my younger brother as a Christmas present, which was the start of many years of buying him McKillp books for Christmas (and reading them myself, once he'd finished). McKillip has been a favorite ever since.
5) Silence by Shusaku Endo. Now we're into books I read in college. This was for a world lit class, historical fiction about a devout Catholic missionary to Japan at a time when it was closing to European influences, including religion. The title refers to the apparent silence from the missionary's God to the people's suffering.
6) San Manuel Bueno, Mártir by Miguel de Unamuno. I read this one in Spain. It's the story of a priest, seen as a saint by his parishioners, but who can't bring himself to believe in everything he preaches. His martyrdom, then, is in feigning that belief.
7) The Brothers K by David James Duncan. A coming-of-age novel about a family of four brothers (and much younger twin sisters), against‚the backdrop of baseball and the Vietnam War. Duncan is a very funny writer, and this book weaves together the voices of the brothers wonderfully (I'm guessing the fact that I am one of four brothers might have drawn me into this even more), and deals with faith and doubt and war and anti-war and family dynamics in an impressive way.
8) Gormenghast books by Mervyn Peake. The shear architectural imagination of these books, the absurd characters, the whimsy and the weight of traditions, and a claustrophobically vast castle, in decay. Originally I read this for my undergrad honors thesis (and I've re-read it since then).
9) Invisible Cities by Italo Calvino. Not for a college class, but based on my advisor's suggestion for my own interest...for which I am very grateful. Calvino is my favorite writer, and this was my first introduction to his writing (and remains my second favorite, close behind If On A Winter's Night a Traveler).
10) The Botany of Desire by Michael Pollan. Now we're into the post-college time frame (yeah, there's no way I can limit this to ten...let's make it thirteen). The subtitle for this nonfiction book is "A Plants-eye View of the World," and I don't think I can say it any better. Seeing how these four plant species have changed and interacted with human history was one of those mind-twisting things that changes how you see the world.
11) Perdido Street Station by China Mieville. I've always pointed to this book as a paradigm-shifting book, where I finally realized just how wide open the field of fantasy can be. I find Mieville's imagination in books like these Bas-Lang books and Railsea to resonate so closely to my own.
12) City of Saints and Madmen by Jeff VanderMeer. At almost the exact same time I read PSS, I read this book (for the first of...4 times, I think). VanderMeer has long been a favorite writer (I'm currently reading his latest, Acceptance), and this book would have been even more paradigm shifting if I hadn't already read PSS. The city of Ambergris with its fungal infestations has stayed with me like few other imaginary places.
13) The Orphan Tales by Catherynne Valente. Difficult to say anything about these books except that they are pure storytelling magic, full of nested stories that feel like fairy tales in all their original power and resonance.
There are easily a dozen more books I'm sure I could pick out, if I were to think about this for any length of time. But these are all definitely a part of my reading DNA.