A lot of fandoms has this myth: that there is one book or show or movie or song that will convert anyone to their cause. It's a tempting theory and I've succumbed to this paradigm on more than one occasion. The cassette tape generation is quite familiar with this concept as audiophiles distribute mix tapes that's supposed to convey "this is who I am," the story of my life in two half-hour segments. Last month, I was told by two friends that Asterios Polyp is enjoyed by readers who don't usually read comics (and more than a decade ago, I gave away around a dozen copies of The Dream Hunters to friends and acquaintances). There will be multiple variations of this: "D&D introduced me to RPGs," "My Neighbor Totoro is universally loved," "The Lord of the Rings got me into fantasy," "If you're into horror, you must watch Ringu or read Uzumaki".
When it comes to genre fiction, the book you can recommend to anyone is the Holy Grail. Sorry, as much as I love Peter Jackson's The Lord of the Rings, J.R.R. Tokien's writing was a poor fit for me. C.S. Lewis felt too didactic. Philip Pullman too polarizing. Some found J.K. Rowling too mainstream (as if that's a bad thing), too young adult (whatever that means), too mediocre (fair enough). For quite some time, A Game of Thrones was my go-to-book--until my Filipino teacher said he hated it because the modern language proved too jarring for his suspension of disbelief. Nowadays, The Lions of Al-Rassan and Tigana are the books I give to people who are looking for epic fantasy without the investment of reading a decade's worth of fiction. On second thought, Dune might come in handy as well.
But the problem is that none of those books will work for everyone. Different stories call out to different people. If I'm in the mood for love and a sense of loss, I recommend Tim Pratt's "Little Gods" or Dean Francis Alfar's "L'Aquilone du Estrellas (The Kite of Stars)" (although Peter M. Ball's "Say Zucchini, and Mean It" is catching up on that list). I can recommend Kij Johnson but each story works for a different reason: "Spar," "26 Monkeys, also the Abyss," and "The Empress Jingū fishes." There's also lots of short story authors (who are personal heroes) that I'd recommend--each one different and contributing something unique to the field: Mary Robinette Kowal, Jeffrey Ford, Claude Lalumiere, Paul Tremblay, Karen Joy Fowler, Theodora Goss, Aimee Bender, Kelly Link, Elizabeth Hand... (and I haven't even gotten to the local authors we have here that you never heard of: Nikki Alfar, Andrew Drilon, Crystal Koo, Francezca Kwe, Mia Tijam, Kate Osias, Ian Rosales Casocot, etc...)
Lately, I've been more of the type that gives a wide variety of books or comics, and then narrow down my recommendations based on how they react. Like Kelly Link? Maybe you should try some Aimee Bender of Theodora Goss. Like George R. R. Martin? Have you tried Robin Hobb or Daniel Abraham? Unfortunately, this also entails a lot of rejections. Sorry, that wasn't my type of book. It bored me. Not my genre. And you know what, that's fine. Don't take it personally (that's also valuable advice to writers). The point is to explore the boundaries of your friends and acquaintances, discovering what really interests them, or better yet, introduce something new to their diet. (Unfortunately, this results in me lending out or giving away a lot of books, with my intentions sometimes suspect.)
So, my question is, what are your favorite books that you automatically recommend to everyone you meet? Or are you an astute bookseller, probing for their tastes and interests before recommending a book?