There is hope
As a Christian you already know that there's nothing on earth that can really satisfy your soul so you stop seeking delight in the world. The problem comes when you fail to seek delight in the Lord (or don't know how to fight for it) because then you see yourself in a spiritual numbness where you are not getting joy at all. Life becomes gray. Everything losses its attractive.
This book helps you fight for joy by delighting in Jesus's glory, by striving for getting your soul satisfied in Him, in his beauty.
I highly recommend this book to anyone struggling with sadness, depression or lack of joy and purpose in life.