I've been eagerly anticipating publication of this book since before I started dating my wife, made first contact with the church where I now pastor, got married, moved halfway around the country, and had three children. Which in my universe is, well, just over three years, actually. (We had twins.) But it felt like much longer.
On several occasions in the past couple years I've referred to a chapter written by Steve Wellum, one Kingdom Through Covenant's co-authors, which formed the backbone—literally and figuratively—of Tom Schreiner and Shawn Wright's book on baptism. That chapter is available for free here. I've also just listened to a dense, provocative lecture by Wellum on the relationship between limited atonement and Baptist ecclesiology. (The best part of that lecture was Wellum pointing out how Reformed (non-Baptist) ecclesiology is actually incompatible with limited atonement, much to the consternation of his forthcoming book's Presbyterian publishers.) I wouldn't be surprised to see some of that material in Kingdom Through Covenant as well. I'm less familiar with Gentry, but somewhere out there is an insightful lecture from him on what holiness is, as the language is used in Scripture, not pop theology.
All that to say, I suspect that Kingdom Through Covenant is a volume that'll be quite helpful to those of us who perceive significant unresolved problems with both the dispensational and covenantal systems. How well it answers those questions remains to be seen, but I'm confident that it'll delve into some of the issues and texts that apologists for those systems too often avoid. Because of that, I hope even theologians who disagree will engage rigorously with its arguments.
I haven't found it on the WTS site yet, but Amazon lists it at a remarkable price for an 850-page hardcover, though there's some speculation this may be an introductory, limited-time offer.
And finally, as he always does, Justin Taylor has quite a bit more info and some links here, including lengthy quotes from both Wellum and Gentry outlining problems with the Christology and meta-narrative of the two traditional systems.