This purports to be a book on spiritual warfare, but it veers from that purpose into being a book about demon possession and the proper way to exorcise a demon. Which would be fine, but Anderson actually says several times that we shouldn't engage demons when we encounter them, then turns around and does the exact opposite in the examples he provides of "possessed believers" he's encountered.
My problems with this book are many, but my three biggest problems with it are these:
1. Anderson explicitly claims that Christians can become possessed, and at one point seems to claim that the Apostle Paul was possessed. The actual examples of demon possession in the Bible always follow a certain pattern, though. First, there is shown to be a demon (and it is always explicitly referred to as such). Then Jesus or an apostle casts out the demon. And finally, as a result of the experience, the former possessed person accepts Christ's salvation. We are never (to my admittedly fallible knowledge) given any examples of possessed people being believers before the possession began, or coming to faith during their possession. Anderson uses his own interpretations of verses to uphold his claim, often with no explanation of why he believes his interpretation is correct. This is fallacious, and dangerous, and I dislike that he continues to use this line of reasoning the entire book.
2. The number of possessions he claims to have seen. Anderson claims to have witnessed an inordinately high number of possessions. At one point he claims to have cured someone of MS by casting out a demon that had been causing her symptoms. A little later, he claims to be the only one who was able to help a woman who had been a medium, because the other counselors she'd seen "were just trying to manipulate the spirits--which was what she was trying to do when she was a [...] medium." That is a direct quote from page 112. Christian counselors were trying to communicate with demons and manipulate them like a psychic medium. I find this a ridiculous claim, and it was, sadly, one of many examples shared of times when Anderson was able to "help" when no one else could. I am dubious that any single man could encounter that many cases of true possession.
3. The dismissive attitude Anderson has toward depression. As someone who suffers from depression, Anderson's attitude toward it was insulting and dismissive. He often implied that depression was just a symptom of laziness or being weak-willed, and that if depressed people would just stop being lazy they'd feel better. (This is not my impressed face.) Along with this, he later deliberately phrased an entire paragraph to make it seem like people who asked God for help resisting temptation/sin would be dismissed by God because (to quote what Anderson claims God says), "'I've done all I'm going to do. I defeated and disarmed Satan at the cross. I conferred all authority on you in Christ. Now open your eyes. Realize who you are and start living accordingly.'" (p. 87)
What statements like these do is put all the responsibility for righteousness, sanctification, and remaining sinless on believers, which is not at all biblical. For people already struggling in their faith, telling them it's all on them and God's not going to do anything to help them is maybe the single most damaging thing you could say.
In addition to these three things, there is also the fact that the first time I tried to read this book, I kept having the thought "I need to cast out whatever demon is inside me," quickly followed by, "But I'm not demon possessed. I don't have any of the biblical symptoms of possession. I have depression and anxiety, but I'm not blaspheming the name of God, and I'm not foaming at the mouth. I don't speak in tongues, and I don't try to physically harm myself. I'm just sad for no reason, or scared for no reason." Anderson's teaching that our emotional ailments are rooted in some kind of spiritual warfare is dangerous. It's going to lead Christians to believe they're demon possessed (they aren't) and it's going to confuse and mislead people who are having success treating their mental illnesses with medication and therapy.
EDITED TO ADD:
I went back and looked at the "pray away the demons" part of the book again, having just skimmed it the first time through and I need to add to my review that Anderson has several lists of things that he says are demonic. Included on these lists are things like Magic: The Gathering card games and playing Dungeons and Dragons. He also lists several things that are morally neutral, but depending on how you participate might be good or bad. However, he claims that any kind of participation in these things is demonic.
He also has a section talking about renouncing your sexual sins. He lists being raped or molested as a sexual sin. Not raping or molesting but being the victim of these crimes. He then orders readers to ask God for forgiveness for being raped/molested, and tells them to ask Him to reveal if they were secretly willing participants in their sexual assault. This is some of the most blatant victim blaming I have ever seen, and Anderson tries to make it sound like God sanctions his ideology. Nowhere in the Bible is any victim of rape ever told that it is her fault. Nowhere in the Bible does God ever shame someone for being raped. Please be aware that this triggering language is included in the book, and that it is wrong.