John Stevens addresses a lot of questions regarding this topic of doubt, and he did a great job laying out scripture to provide clarity. Doubt isn't a bad thing, but Stevens emphasized on multiple points that we must deal with it so it does not develop into unbelief. As Stevens pointed out, even Jesus was tempted in the wilderness by satan to doubt---His identity, His protection, His mission---and He sympathizes with us in our weakness (Heb 4:15.) I had never before noticed that Jude 22 says to "be merciful to those who doubt." When we or someone we know asks hard questions, there's no need to accuse or belittle. But it does need to be dealt with. This book really helps with why and what that looks like.
The most impactful part for me was when he talked about how to know if we are really a Christian. I've struggled a little because I have no idea when I became a believer; I know that I know Jesus now, but shouldn't going from death to life have had more of a noticeable change in me at a specific point in my history? Stevens made the point that "God does not promise equality of spiritual experiences to His people." What happened for one Christian doesn't mean it's been promised to happen to me as well. We can be assured that we have the Holy Spirit through such unremarkable instances as: "Every time we are disgusted by sin, every time we are grateful to Jesus for what He has done for us, every time we hunger to be more holy, every time we choose to follow His ways rather than our own---these are experiences of the work of the Spirit in our lives, and signs that we truly belong to Him."
It's a good book, but I felt it was a little dry at times and I think the author would've done well to share more stories or illustrations as this book didn't keep my attention as Jeramie Rinne's book in this series did (my review here.) For a more thorough book on assurance, I recommend Paul Washer's book Gospel Assurance and Warnings (my review here.)
Disclosure: I received this book in exchange for an honest review.