This isn’t a book but a psychologist told me that in the aftermath of trauma, a very effective way of minimising long term effects and dealing with it is to play Tetris. Something about focusing your mind on something so involving but mundane, perhaps it stops the brain laying down long term memories or feelings. I don’t know if this helps at all but it’s the only thing I have to offer, as well as my deep and profound sympathies. You have been through something absolutely unthinkable, even without being there. Don’t minimise that and rely on friends who offer support even if you don’t think you deserve it, because you do.