All Otaha Higuchi wants to do is work with books. However, the exhausting nature of her work at a chain bookstore, combined with her paltry salary and irritating manager quickly bring reality crashing down around her.

She is on the verge of quitting when she receives a message from somebody calling themselves 'Seven Rainbows', inviting her to apply for a job at a library with no name, a place referred to simply as 'The Night Library'.

After successfully passing the interview, Otaha arrives at The Night Library and her sunny personality immediately earns her comparisons with Anne of Green Gables. For the very first time she feels she has found her place in the world. As well as a treasure trove of books, the library houses a group of likeminded literary misfits, including a legendary chef who prepares incredible meals for the library's employees at the end of each day.

Together they embark on a series of bookish adventures. But when the library's mysterious owner decides to temporarily close the library, Otaha and her friends fear that it may not reopen and that the peace they have found there will be lost to them forever. 

Is their friendship and their faith in the value of books strong enough to save it? And what will remain if it isn't?