He makes a number of excellent observations about the book, but his first sentence is a bit strange. He says that this book is "the first attempt of which I am aware to present at a non-academic level a book-length biblical and theological case for 'two-kingdoms theology.'" This is very, very strange, indeed. Mainly because this book (which I do not recommend) was published in 2009 by... oh, who was that? Oh, yes. Ligonier Ministries. The organization for which Keith Mathison regularly writes.
I am still a bit perturbed that Ligonier published it. In the spirit of being nice, I'll just say that I don't think it is a good book. At all. So, stick with Dr. VanDrunen if you want a presentation of "Two Kingdoms" theology from someone who understands the issues and compellingly (if still unpersuasively) presents his case.