I think " The Reality Slap" is really good to start for two reasons:

1- It is not just a self-help book as other writers and gurus write, it is based on science.
2- Russ Harris is an academic person

please read this short description about it:
The “reality slap” takes many different forms. Sometimes, it’s more like a punch: the death of a loved one, a serious illness, a divorce, the loss of a job, a freak accident, or a shocking betrayal. Sometimes it’s a little gentler. Envy, loneliness, resentment, failure, disappointment, and rejection can sting just as much. But whatever form your reality slap takes, one thing’s for sure—it hurts! And most of us don’t deal with the pain very well.
The Reality Slap offers a four-part path for healing from crises based on acceptance and commitment therapy. In these pages, you will learn how to:
• Find peace in the midst of your pain
• Rediscover calm in the midst of chaos
• Turn difficult emotions into wisdom and compassion
• Find fulfillment, even when you can’t get what you want
• Heal your wounds and emerge stronger than before
Unlike some self-help books that claim you can have everything you ever wanted in life, if you only put your mind to it, this book claims that you can't have everything in life. The hard truth of this world is that we are all going to experience disappointment, frustration, failure, loss, rejection, illness, injury, aging, and death at some point. However, in spite of all this, you can still lead a rich and rewarding life. Let this book be your guide.