Fiction book about grieving a loved one

My (24F) sweet cousin (24) unexpectedly passed away a few days ago. I have never lost someone so close or so out of the blue. I am a huge Harry Potter fan and I love how it deals with death and grief, but in a way that makes me feel like I can get through it, if that makes sense. I am looking for other fictional books with similar themes and messages about death, loved ones, etc. Thank you.