I haven't read it, but I am inclined to do so. I'm nearly finished his The Thirty Years War: Europe's Tragedy and I've been really impressed by it. While one good book doesn't guarantee the quality of the others, especially as Heart of Europe ventures a bit beyond his usual comfort zone, I'm willing to trust the quality of his scholarship enough to give it a try.

Wilson has tackled a very large and complex subject, and he does so in a unique approach, combining chronological and topical approaches. Both have their advantages and disadvantages, and by explaining many things using these two different approaches, I find that Wilson has helped me understand things that would otherwise be difficult to appreciate.

The downside to this dual approach is that some topics seem to be impenetrable in the first few chapters, and repetitive in the last few chapters. But for such a complex topic, I can't really blame him. Overall I highly recommend this book, I really enjoyed it.

The TL;DR: The HRE is not the weak, ineffective, corrupt polity that many have made it up to be, but rather a highly adaptive and malleable one. To understand this is an arduous journey, but one that's worth it.