Over 100 Weeks on the New York Times Bestseller List! On 44 State Award Lists! Discover what James Patterson calls "the coolest library in all the world" in this fun-filled, action-packed bestseller from the much-loved coauthor of I Funny and Max Einstein! "A worthy successor to . . . Willy Wonka." -Booklist, starred review 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, Mr. Lemoncello's All-Star Breakout Game, and Mr. Lemoncello and the Titanium Ticket! "Full of puzzles to think about [and] puns to groan at . . . this solid, tightly plotted read is a winner for readers and game-players alike." -Kirkus Reviews, starred review