Suggest me a book as someone grieving the sudden death of their boyfriend

My boyfriend passed a week ago from shitty and sudden circumstances. I feel a lot of guilt and confusion and pain and sadness. I have so many regrets about our relationship and ways that I could’ve been better for him. It’s hard for me to grasp that he’s gone and we don’t get another chance together.

Could use a book about partner loss or just views on death in general and how to cope. TIA <3