The Lost Library is a middle-grade novel published in 2023 and cowritten by Rebecca Stead and Wendy Mass. When a little free library suddenly appears in the town of Martinville, fifth grader Evan is pleased. However, when he discovers the books it offers are from the former town library, which was destroyed in a fire over 20 years previously, he sets out to discover the mystery. Along the way, Evan learns about the power of books and of secrets and conquers some of his fears about growing up.

Mass has published 31 novels for young readers, many of which have been translated into numerous languages. She has received 92 state awards and was honored as the New Jersey Association of School Librarians’ 2018 Author of the Year. One of her novels, Jeremy Fink and the Meaning of Life, was adapted as a 2012 film. Stead has authored seven books for young readers. She has also received numerous awards, including the Newbery Medal, the Boston Globe/Horn Book Fiction Award and Fiction Honor, and the Guardian Children’s Fiction Prize.

The Lost Library marks Mass and Stead’s second collaboration; the two also coauthored Bob (2018). Its chapters alternate between two narrators named Bob and Livy, one author writing Bob’s chapters and the other writing Livy’s chapters. In an interview, Stead explains that The Lost Library was written much more collaboratively (“Mackids Spotlight: “Rebecca Stead and Wendy Mass.” Mackids School & Library, 31 July 2023).

This guide is based on the 2023 hardcover edition by Feiwel and Friends.

Plot Summary

One night a little free library appears outside the History House in the town of Martinville. Built from an old cupboard and still smelling like the cheese that was stored there, the library is guarded by a large orange cat whose name, though no one but he knows it, is Mortimer. Mortimer remembers his time spent living in the Martinville Library when he and his sister, Petunia, were kittens. Mortimer has not seen Petunia since a fire destroyed the library 20 years ago; he fears she perished in the blaze.

The novel’s narration alternates between Mortimer, a former librarian nicknamed Al, and a fifth-grade boy named Evan. The end of the school year is just days away as Evan walks to school, sees the new little free library, and takes two books from it. Later that day, he studies the books, realizing that they are real library books, stamped as belonging to the Martinville Library. Evan knows about the library fire and asks his father to inspect the books. When his father responds strangely and runs out of the room refusing to speak about the books, Evan’s interest in the former library is piqued.

With the help of his friend Rafe, Evan collects clues from the library books. They discover that nearly all of the books in the little free library are from the Martinville Library and that they are all stamped with the same due date: November 5, 1999. They later discover that this was the day of the library fire, the cause of which was never determined. Evan is also surprised to find his father’s name on the borrower’s card of one of the two books he took from the little free library. The other book, How to Write a Mystery Novel, was checked out by H. G. Higgins, the famous mystery writer. While Rafe is certain this signature is a joke, Evan wonders if the author actually lives in Martinville. A Polaroid picture inside the book serves as another potential clue. Evan writes a letter to H. G. Higgins, hoping to learn whether he is indeed a Martinville resident.

Al, which stands for “assistant librarian,” lives in the History House with Ms. Scoggin and Mr. Brock. Ms. Scoggin was the library director and Mr. Brock one of its patrons. All three of them perished in the library fire and are now ghosts. Though Al practices being invisible, sometimes children see her when they tour the History House. She takes care of cooking for Ms. Scoggin and Mr. Brock and runs errands as needed. Al often thinks back on her experience as the assistant librarian, recalling one patron in particular: a quiet young boy who was reluctant to interact with any of the other patrons. Though Al invited him to discuss books with the Wednesday Book Club, the boy refused, preferring to read his books alone. In time, however, the boy and Al connected over the books they both liked. The boy grew and eventually secured an internship at the library; it was he who gave Al her nickname.

As their search for the truth continues, Evan and Rafe explore the site of the former library. Evan finds a set of keys there and keeps them. He learns that H. G. Higgins is merely a pseudonym but cannot uncover the author’s real name. A breakthrough occurs when Evan and Rafe decide to search a local treehouse in the woods, discovering that one of the keys Evan found at the library site opens its door. Inside the tree house, Evan realizes that the Polaroid photo was taken from that very spot. He posits that the young man in the photo may be H. G. Higgins. Fifth-grade graduation arrives, and Evan’s parents attend the celebration.

Meanwhile, the interest in the little free library grows, and Mortimer continues to guard the collection. He enjoys interacting with the new patrons. Al, however, grows worried about Ms. Scoggin, who seems increasingly unhappy. Al is surprised when a young boy arrives at the History House asking for her help in obtaining information about the library fire. Al provides the boy (Evan) with newspaper articles and feels useful and fulfilled for the first time. The news Evan uncovers, however, is that his father—then an intern at the library—is suspected of causing the fire.

Evan races home and confronts his father, who insists that he loved the library and its books and denies setting the fire. However, he does reveal that he is H. G. Higgins. Back at the little free library, Mortimer chats with a group of mice who say that Mortimer looks like another cat they know. Mortimer grows excited, hoping this cat might be Petunia. His interaction with the mice sparks an idea, and Mortimer sets in motion a plan to reveal the truth of the mystery to Al.

As Mortimer and the mice set forth to execute their plan, Al sits inside the History House with Ms. Scoggin and Mr. Brock, who suddenly float up into the air. Al grabs them, trying to make them stay, but Ms. Scoggin insists that she and Mr. Brock need to move on, especially now that Al has found her purpose once again. Al lets them go and then reveals that she is not a ghost: She survived the fire thanks to Edward—Evan’s father and the boy who interned at the library—who helped her from the building.

Evan and his father arrive at the History House just in time to witness the mice staging a reenactment of what happened on the night of the fire. A mouse had been running around the basement with a matchstick in his mouth. Mortimer and Petunia chased the mouse, and the match was struck, accidentally causing the fire. Al, Evan, and his father know the truth of the cause of the fire, and Evan’s father and Al are reunited for the first time since that day.

Evan convinces his father to persuade the fire marshal to reopen the library investigation, and the department clears Evan’s father of any wrongdoing. With the money earned from his H. G. Higgins novels, Evan’s father funds the construction of a new library.