The Memory Book by Rowan Coleman
They are not wrong when they say this book [about a woman who discovers she has genetic early-onset Alzheimer's, and how it affects her life and those of her mother, husband, and children] is very moving.
The "memory book" of the title is a notebook given to the main character by her husband, in which she and the rest of her family write down their memories of her in order to help her remember. It hits very close to home at the moment and I cannot read it without weeping.
The sub-plot about Ryan gets me every single time.