There is much good in this book; if you need some practical advice on how to proceed in a dating/romantic relationship or how to evaluate a potential spouse, you will find a lot that is commendable in this book. However, while the specific applications can be quite helpful, the exegesis behind them is seriously flawed.
The basic foundation of everything in this book is Matt 6:33 – “But seek ye first the kingdom of God, and his righteousness; and all these things shall be added unto you.” There is of course nothing wrong with using this passage. What is wrong is how Thomas reads/applies the passages. In context, “all these things” is referring to certain specific things that Jesus has been teaching on but Thomas doesn’t care. For Thomas, “all these things” is whatever you might want in a relationship, but especially it is a successful marriage to a faithful, loving spouse. There may be a case to be made that marriage is included in “all these things” but Thomas never makes that case, he simply assumes it. This, at best, is a case of correct doctrine from an incorrect starting point. At worst, it is a twisting of Scripture.
Thomas mentions more than once that his advice doesn’t guarantee a successful marriage, but his applications constantly are presented in a manner that seem to imply the opposite. This can be a very difficult balance to strike, between showing that generally one thing is true but and therefore you ought to build your life around that generality without giving the impression that it is an absolute, but in my opinion, Thomas simply doesn’t have that balance at all. A few disclaimers don’t equal balance.
While I agree with much that is in this book, it simply is not a good book to turn to.