That freestanding wall of sticky notes in the North Concourse of the Javits lobby is your opportunity to post a message and meet Matthew “Levee” Chavez, the artist responsible for that headline-making wall of anonymous 3-inch×3-inch sticky notes in the New York City subway system the day after the 2016 presidential election.

A self-described “unlicensed subway therapist,” Chavez is at BookExpo to promote Signs of Hope: Messages from Subway Therapy (Bloomsbury, Oct.), which includes a selection of the thousands of sticky notes that were posted last fall. He’s planning to donate a portion of the proceeds from the book to the ACLU and to Win, the largest provider of shelter and services to New York’s homeless families.

After a motorcycle accident in 2015 while visiting a friend in Indonesia left Chavez hospitalized for three weeks, he thought about “how people feel better after feeling bad.” In December of that year he relocated to New York after spending a few months in California, where he worked as a substitute art teacher in charter and private schools, and as voiceover talent doing audio book narrating. “Nothing you’d know,” he laughs, asked for titles. “Legal productivity software manuals.”

Within months of the move, Chavez created the persona of “Secret Keeper” and set up a table in the Montrose Avenue subway station in Brooklyn. He invited people to write their secrets in his notebook. “But,” he says, “a lot of people wanted to have conversations instead, and at the end [they] would say, ‘This is like therapy.’ So I bought a brown suit and a certificate of achievement from the Dollar Store to see if people would talk to me. It was awesome. I’d rarely sit for more than five minutes before someone would come to talk.”

But the day after the election, Chavez was met with silence. People were speechless. So he went back to his original notebook idea and bought pens, markers, paper, tape, and sticky notes. “At 2 p.m.,” Chavez says, “I went into the 14th Street station at Sixth Avenue. There’s a tunnel connecting the 1,2,3, F, and L trains, and people hate it. But I love that tunnel. There’s not a lot of train sound, and you can have conversations there. I wrote ‘Express Yourself’ and a note saying, ‘I’m sad and my friends are upset.’ People started writing on the sticky notes. I just sat there. After a while I had to step away. Between 2 p.m. and midnight, 2,000 people wrote on sticky notes. It was beautiful to watch.”

Video of the phenomenon went viral, and that evening, television news reporters arrived to interview Chavez. His main concern was the notes. “I didn’t want them to be vandalized,” Chavez says, “so I took them all down, which took me until 2 a.m. The next day, when I arrived at 2 p.m. to put the notes back up, there were 400 sticky notes already up and a bunch of reporters waiting.”

During his time in the station, Chavez was approached by several book publishers. He would like Signs of Hope to bring people together, no matter what their gender identification, politics, skin color, ideology, or sexual orientation. He hopes people will read the notes and not feel so alone.

Chavez also has a contract for a second book for children. He is writing it, he says, “[to] encourage young people to be active in their community. I believe that everyone is responsible for influencing their own environment.”

As for the original sticky notes, which Chavez removed from the subway station on December 16, the New-York Historical Society is preserving about 4,000. A selection of them were recently exhibited as art installations at Arcadia University Art Gallery, in Glenside, outside of Philadelphia, Pa., and the Herbert F. Johnson Museum of Art at Cornell University in Ithaca, N.Y.

Visitors can post their notes on the wall Matthew Chavez has set up in the North Concourse of the Javits Center.