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.

Under my 'WHO ARE YOU?' the blue pen wrote: 'Not yet. If I tell you, you'll picture someone, and then I have to live up to the picture.' 'Finish the book with me instead. I only reply to notes. Deal?' Below that, they underlined a sentence in chapter 9 and wrote: 'Start here. Tell me you didn't cry.' I did cry. In 2019. In a laundromat. Deal.

Chapter 15, a blue note stops me cold: 'Real question. Why did you give this book away? People don't leave their favorite book in a box on the street for no reason.' They're right. There was a reason. I sit with the pen for a long time. Then I write it: 'Someone used to read it to me. They're gone now. I couldn't look at it — but I couldn't throw it away either.' I return the book. Slowest three days of my life.

Three days later the book is back, rubber-banded to a second, thinner book. Poems. In mine, under my note, the blue pen wrote: 'Thank you for telling me. Books that hurt need company. So do people. Page 33 of the thin one is yours now.' Page 33 is a poem about a door left open. Under it, small: 'I'm the one who leaves the box door open every morning. That's me saying hi. Come say it back sometime.' I did. Hello is easy when someone's already read your margins. The box door stays open. Both of us check. Every morning.