First of all I was going to go with The Fault in Our Stars by John Green, being the most recent book to require tissues, but that's perhaps too obvious, and no doubt you have all read it already. So instead I will go with the book that caused me to, literally, sit up all night reading through tears: Rilla of Ingleside by Lucy Maud Montgomery.
The final book in the Anne of Green Gables series is quite a departure from the rest of the books, and devastating for many reasons. By this time, Anne Shirley has been happily married to Gilbert Blythe for over twenty years, and has six grown-up or teenage children. But it is 1914, and the world is about to change forever with the outbreak of the First World War.
As you might guess from the title, Anne Shirley is not the focus of this novel. She is always there, but in the background, while the novel concentrates on her children, especially fifteen-year-old Rilla, and nineteen-year-old Walter.
Rilla is a very bittersweet read, especially if you think back to the beginning of Anne's tale as the ever-optimistic, imaginative redhead in a timeless village community. The war brings Anne and the Blythe family into the real world, and reality hits hard. How can Anne's story end with such heartbreak and devastation? But Rilla is an outstanding piece of writing, a contemporary study of World War 1 from the point of view of those left behind, the families who had to watch from afar, to carry on with life and hope that their loved ones would return. It also works as a stand-alone novel. It helps to have read the previous books in the series, but it is not essential.