The Library of Borrowed Hearts by Lucy Gilmore

A.J. Fikry meets The Bookish Life of Nina Hill in this charming, hilarious, and moving novel about the way books bring lonely souls together. Two young lovers. Sixty long years. One bookish mystery worth solving. Librarian Chloe Sampson has been struggling: to take care of her three younger siblings, to find herself, to make ends meet. She's just about at the end of her rope when she stumbles across a rare edition of a book from the 1960s. Deciding it's a sign of her luck turning, she takes it home with her―only to be shocked when her cranky hermit of a neighbor swoops in and offers to buy it for an exorbitant price. Intrigued, Chloe takes a closer look at the book only to find notes scribbled in the margins between two young lovers back when the book was new…one of whom is almost definitely Jasper Holmes, the curmudgeon next door.