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 flip to the inside cover and write it big: 'WHO ARE YOU?' Then, smaller: 'Your notes are better than the book. And this is my favorite book.' I put it back in the box before I can chicken out. Three days. Nothing. Day four, the book is back. There's blue ink under my question.

The blue pen answered with a name. 'I'm Sam. The gray house with the terrible lawn — that's on me, not the lawn's fault.' 'I found your book on my worst week and your notes felt like company. I wrote back before I could stop myself.' 'You don't have to do anything with this. The margins are enough. But now you know.' A name and a house. Forty steps from mine.

I don't write back. I walk. Forty steps, one deep breath, knock. Sam opens the door holding — I swear — the same blue pen. 'You're black-pen,' Sam says. Me: 'You're terrible-lawn.' 'It's a fixer-upper.' A pause. 'So was my week, when I found your book. Come in? I have questions about page 88.' I stayed two hours. The lawn is still terrible. We read on the porch anyway, most evenings, trading one pen back and forth.