There's a little free library on my street. A wooden box on a post, holds maybe ten books. Last month I left my favorite book in it — the copy with all my notes in the margins. 'This line got me.' 'Nobody recovers this fast.' 'I'd forgive him too.' Today it's back. Same coffee stain on page 41. But under every note of mine, someone wrote back in blue pen. Under 'I'd forgive him too' it says: 'You would? I've been arguing with you about this for a month.' I don't know this handwriting. I check the street. Empty.

I take it home and grab a pen. Under their 'You would?' I write: 'Forgiving isn't the same as forgetting. Page 200 proves it.' I answer every single reply. Little arguments. Little agreements. On the last blank page I write: 'Your move.' Next morning I put the book back in the box. By noon it's gone.

Two days later the book is back. Every note answered. Under my 'Your move' they wrote: 'Okay. New rules. You pick the next book. Anything. I'll read whatever you love.' Then, smaller, like they almost didn't write it: 'This is the best conversation I've had all year.' Me too, stranger. Me too. But now I have to pick a book. And a book says a lot.

I panic and go weird: I leave a cookbook. 'Soups of the World.' On page 30, under a lentil soup, I write: 'This one got me through last winter.' It's a test. Anyone can be deep about a novel. Let's see them reply to soup. Five days later the cookbook is back. Page 30, blue pen: 'Made it. Burned the onions. Started over. Worth it.' And tucked at chapter 4: a folded index card. A handwritten recipe. Titled 'Mine.'