I'm prone to love almost any idea based in the sharing of books or what we're reading. If I have to engage in small talk, "what are you reading/OMG you should read" is my comfort zone, and I find the idea of leaving surprise books for people ridiculously appealing. I've been itching to install a tiny "library" in public for more than a year, and when I noticed these trellises in a high-traffic area outside my local Caribou Coffee, I finally decided to make it a priority.
The library itself is actually just an inexpensive mailbox purchased from Home Depot and appropriately decorated. It doesn't hold a ton of books, but it's the perfect size for something that may wind up stolen or taken down by stodgy property management (like my last public installation, which disappeared in less than 24 hours). Maybe this is just a trial run for filling this tiny space with books!
I tucked the following books into this library: Pattern Recognition by William Gibson, The House of the Spirits by Isabel Allende, Coraline by Neil Gaiman, The Secret Garden by Frances Hodgson Burnett, and The Magician's Nephew by C.S. Lewis. This means I can buy more books, right? (P.S. I did.)
If putting up your own tiny library seems like too much effort, consider something like BookCrossing and leave a copy of a book in a random location.