Braving the Wilderness: the quest for true belonging and the courage to stand alone by Brene Brown is a universally appealing book. Who hasn't felt like they did not belong at some point? The short of it is pretty simple, to feel like you belong you have to be yourself. The book touches on other topics related to belonging like self-worth, anxiety, and depression. It's part personal anecdotes and part research. It's a delightful read (or listen! It's read by the author).
Running with Mindfulness by William Pullen is a good self-help book that gives new meaning to the phrase "running is my therapy". This book provides lots of rhetorical questions to ponder while running. Questions that relate to your relationships, anxiety, depression, anger, stress, etc. The book also explains how Dynamic Running Therapy (DRT) works---combining mindfulness and movement.
Man's Search For Meaning by Viktor E Frankl is a life changing book that everyone should read. The book is in two parts. The first is a description of Viktor Frankl's life and mindset in a Nazi Concentration Camp. He describes how finding meaning in the most grim of circumstances provides hope and a reason to live. The second half of the book is his theory and practice for "logo therapy" (existential therapy). For context's sake, Viktor Frankl is a significant player in the history of psychology and therapy, as he presented a different perspective than the well known Sigmund Freud. Frankl presents a theory of behavior and mind based on finding meaning in life. Freud's theory in contrast focused on motivational drives.
As a therapist I often recommend this book to clients that have suffered terribly from abusive relationships, drugs/alcohol, divorce, grief, depression, etc. What I find is that it leads to a sense of hope and accomplishment that we can (and do) overcome the most challenging and heart wrenching of experiences. Every time I read this book, I personally come away feeling in awe of the human spirit.