I once found a book in a tree.
It was one of Patrick O'Brian's nautical novels, and someone had wedged it in the crook of two branches, just high enough for me to reach if I stretched. I don't know if they left it there hoping that someone would see it and take it, or if they had hidden it there hoping that no one would find it. It seemed quite a landlubber-y place for an O'Brian book to end up. I took a picture of the book, left it there and walked on.
A friend who lives in Ireland once found a book in a seat pocket of an airplane. "The fantastic thing about this book is that it has two boarding passes as bookmarks inside from the previous reader," she wrote me. "One for Yeti Airlines (yes, seriously), with a stamp from Bharatpur (no idea where that is, will have to look it up). And one for Buddha Air, Flight 606. This book is absolutely calling me."
She took the book with her, read it, and then mailed it to me with the provision that when I was done with it, I send it on. "I have this idea of this book traveling the world," she wrote.
The book was about a Brit who manages a Holiday Inn in Tibet ("Running a Hotel on the Roof of the World," by Alec Le Sueur). I liked it so much I bought two copies for friends, then mailed the original to a friend in western Canada, urging her to send it on when she was done with it.
That was in 2008, and for all I know the book is traveling still.
There are so many ways to give books. Yes, you can buy one and wrap it up and leave it under a tree or next to a birthday cake, and I hope you do, over and over throughout your life.
But you can also be mysterious, leaving beloved books where strangers might happen across them. There are, of course, plenty of Little Free Libraries, and that is one way to do it. But I also like the creative, more subversive ways. (Though perhaps the crook of a tree is too subtle.)