hey guys need a book suggestion for my mourning father (50)

hey so my father is 50 years old, his sister died recently, she died of multiple myloema, my father had suffered from hypertension and anxiety all his life and especially someone's death, way back a close friend of him died of cancer so he also got a trauma from it , and my aunt and uncle both died recently uncle died first, it did not effect him that muc, but now aunt had no one, they had no children, also that aunt was my fathers favorite sister, doctor 5 years back had said that she survive 5 years max to max, and after uncs death aunt was also critical my father tried every way possible, putting in all resources and networks available to cure her but wasnt able to and she died a rather peaceful death the whole episode of taking aunt from hosptiatl to going to pharmacies to bring meds at late nights and, now he said that he got a bit of ptsd from that and now he literally gets shocked when hears ambulance and or sudden phone calls, and now hw is even more depressed, it has been months since aunt died, he is happy on the outside but you can sense his grievance. that aunt had a soft corner because she was the youngest elder sis he had shared a very close bond, and also she was unable to bear a child

he has accepted her death but isnt able to get over it