Aside from being overwhelmingly needed, Chan's book is a great combination of devotional and theological. It's almost Puritanical in that you can't divorce the two in nearly every chapter.
He writes with relevance, awareness, and pastoral sensitivity. He also includes examples from the lives of other believers that are encouraging and hope-giving.
Chapter 1 begins by citing Tozer:
We may as well face it: the whole level of spirituality among us is low. We have measured ourselves by ourselves until the incentive to seek higher plateaus in the things of the Spirit is all but gone. We have imitated the world, sought popular favor, manufactured delights to substitute for the joy of the Lord, and produced a cheap and synthetic power to substitute for the power of the Holy Ghost.
By grace, Chan remedies this challenge in his book. It is even seen in the book's summary subtitle: "Reversing Our Tragic Neglect of the Holy Spirit."