Overdue Book

Overdue book is a recurring item throughout The Commonwealth of Fallout 4. When one is returned to one of the book return terminals in the Boston Public Library or East Boston Preparatory School (probably in more locations), the player receives five book return tokens. The tokens can then be exchanged for a variety of prizes. The most notable of which is a copy of the Massachusetts Surgical Journal from terminal in Boston Public Library.

Locations

 * Six of them can be found distributed throughout the Boston Public Library.
 * Three in the mechanical room, northwest corner of library, on the floor
 * One in the women's restroom in a stall
 * One in the main reading room on a shelf
 * One in the secondary reading room on a desk
 * Three can be found in the Pulowski Preservation Shelter at the South end of Trinity Plaza
 * One can be found down the stairs at the east end of the main room of Trinity Church, located at Trinity Plaza. Another down on the bottom floor on the table.
 * One can be found in the laundromat in Lexington, next to the diner.
 * Two can be found inside the ArcJet Systems building and can be picked up during the quest Call to Arms. One is sitting on the large table in the meeting room, which is located behind a closed door off the hallway where you encounter three machine gun turrets attached to the ceiling. The other is in ArcJet Engine Core, in the room just behind the control room for the XMB Rocket. It is located in a Large Toolbox protected by a Novice level Lock.
 * One can be found beneath the counter at the Walden Pond gift shop.
 * One can be found on the lower level in the Kendall Hospital.
 * One can be found on the lower level of USAF Satellite Station Olivia. It's resting on a cabinet in the middle of a small room. The room is across from a partially collapsed wall section off the larger two-story room with scaffolding.
 * One can be found in Faneuil Hall.
 * One can be found in a trader's shack west of Ranger cabin.
 * One can be found in the Mass Fusion building, on the seemingly unreachable section of the fourth floor. You can drop down to the section from the fifth floor.
 * One can be obtained from Daisy of Daisy's Discounts in Goodneighbor. Ask her for work, and she will ask to clear out the super mutants holed up at the Boston Public Library. She'll give the book as a reward when the job's done.
 * One can be found in Covenant, in a toilet behind the house with Penny Fitzgerald's store and Doctor Patricia's clinic.
 * One can be found in East Boston Preparatory School, on the counter in the first room on the right.
 * One can be found during The Big Dig quest. After you've sprung Mel out of jail and reconvened at The Dig, check the seats of the subway cars parked at the platform for it.

Book return terminal prize list
This is a complete list of all prizes available from the Libraries' two Book Return Terminals.