When Kyle learns that the world's most famous game maker, Luigi Lemoncello, has designed the town's new library and is having an invitation-only lock-in on opening night, he's determined to be there! But the tricky part isn't getting into the library⁠—it's getting out. Because when morning comes, the doors stay locked. Kyle and the other kids must solve every clue and figure out every secret puzzle to find the hidden escape route! Don't miss bonus content in the back of the book⁠—extra puzzles, an author Q&A, and more! And look for the puzzle-packed sequels⁠—Mr. Lemoncello's Library Olympics, Mr. Lemoncello's Great Library Race and Mr. Lemoncello's All-Star Breakout Game!