I would like to write a book and publish it on my brothers life. He is a homebound person since age 17 and now is age 58 and suffers from a variety of mental and physical conditions like severe panic attacks, severe depression and many other painful symptoms. He is a farmer, owns 100 acres of black muck and lives off his crops but is very poor. I struggled for years getting medical help to come to the home from dentist to doctors of all types and therapists. One doctor told me to write his story but he has since died and no one every cured him. His whole life is rather depressing and not fun as there is no happy ending here only that he is alive but not well and not sure how long he will live without using today's methods of medicine. Is this book worth writing? Would anyone read such a story of struggles after struggles?
If you look at literary fiction, there is an abundance of hard lives and unhappy endings portrayed there.
But you do not have to make it a depressing book. You can focus on the strength of your brother that keeps him going and persevering despite his difficult fate. Or you can use your brother's story to reflect on the grace of God. Or you can write a parallel account of another life and find meaning in the differences. Or a hundred thousand other interesting things.
Whether or not anyone will want to read your book, will depend on the power of your artistic vision.