Piper's beloved great-grandmother has died, and she is attending the internment. An aunt pushes her to be the first to put the dirt in the grave, which, she finds, means that she inherits the house. When she comes down for breakfast the next day, she finds an elf sitting at the table.
He -- Aelvirum -- tells her that her great-grandmother was murdered. And is not put off by the doctors' having said it was just old age. She learns that the reason he can come in is that the house's backdoor fronts on Fairy. Which, among its other virtues, is influenced by what fantasy writers write. Aelvirum is very grateful to J. R. R. Tolkien
In our world, Piper holds down a part-time job her aunt got her in a bookstore and cleans up the house, making discoveries, and searching for a manuscript Aelvirum had told her was there. In Fairy, rifts are appearing, and whatever falls into them ceases to exist -- or ever have existed -- and it is somehow connected to what her great-grandmother was doing in her last days.
Rifts appear in the bookstore, a book vanishes from inventory, fairies are spiteful, a dwarf mines because that's what dwarves do, a wedding photo is discovered in an old chest, Piper dreams of herself dressed as a bride, and of the books marching around the room and trapping her on a tower of other books, and much more happens.