If I could get away with it, I'd simply say that the book was short but oh-so-good. But one sentence does not a review make. (Though at times, I wish it could be just that simple.)
Kevin DeYoung's book is on the Holy Spirit. Chances are that if you read Christian nonfiction, you've probably read dozens of books about Jesus, about salvation, or, about the attributes of God. But you've probably not read all that much about the Holy Spirit. (I think less is probably written about The Holy Spirit. And not all that has been written is worth reading.) DeYoung's book addresses WHO the Holy Spirit is, WHAT the Holy Spirit does (also what he has done, what he is doing, what he will do), and WHY the gift of the Spirit was such a GREAT, AMAZING gift to the world, to the church.
I've read longer books on the Holy Spirit, but, this short one does just as good a job, in my opinion. And perhaps its conciseness will encourage readers to pick it up.