I would personally recommend Good Reasons for Bad Feelings
By Randolph M. Nesse
The author digs into the idea that humans may have evolved to a certain extent to have good reasons for bad feelings. Several fascinating cases are cited and it made me realise how feelings can be a warning of something. Maybe a bit like when we eat too much salt or sweet then the body reacts. Emotions could work like that but perhaps in a less tangible way.
