I've not finished this yet but felt like writing it up now. This is a very timely book, coming as it does after many in recent years have been challenging the doctrine of penal substitution. What has been (and to a large extent, still is) a defining doctrine for evangelicalism, there have been a number of challenges to its status by those who claim the term evangelical, on both sides of the Atlantic.
What is so good about this book, though, is not just that they mount a thorough defence of the doctrine, but as the subtitle implies, they revel in its wonder and grace. It makes, therefore, for an encouraging and heart-warming read - which is not something one can say for many (if not most) theological tomes.
The book is in 2 parts - the first an overview of the doctrine from a biblical and historical perspective. The second takes on the specific criticisms. Particularly helpful were ch4 (pastoral importance of the doctrine) and ch5 (the historical pedigree) - these (quite apart from all the biblical and systematic evidence) makes for a compelling case (although i concede that i was pretty convinced already!).
As for the second part, the encouragement was that while they were tackling the likes of Chalke & Mann, Green & Baker, their method was constructive and positive. Again two chapters stick out in my mind - on violence (ch9) and justice (ch10) - both very strong contemporary objections to the doctrine which (particularly the former) in my experience are not taken sufficiently seriously by many traditional evangelicals.
I was mildly amused by the number of endorsements that this book had received before going to press (10 whole pages worth, right at the very beginning!). And you can see more if you go to the useful website that the authors have set up (i originally put a link to it here, but the Amazon spam-filter must have thought i was advertising something dodgy). A search for it will get you to it pretty quickly - it is definitely worth a look. But the endorsements are entirely valid - and i venture to add mine here. This is a book to read, return to and rely on - and i hope it will gain the seminal status it deserves in the years to come.