This book feels like it was written in the format of a high-school history report: facts come one after another, neatly clipped off with few links between consecutive sentences, let alone paragraphs. Oftentimes while reading I have felt I must be judging the style of writing too harshly, and I've gone back to other history books - Scullard, Gibbon, JM Roberts, my own textbook from college, to confirm that yes, something is seriously wrong with the writing in this book.
The shortcomings are difficult to define precisely, but the best way I could describe it would be to say the writing has no life in it. The analogy to a high-school history report is an exceptionally apt one, though at times the exposition does rise to the lofty heights of a wikipedia article.
Consider the following paragraph (p98):
"Because of the intertwining of religion and politics, what began as a movement for Church reform became entangled in princely rivalries in the German states. As the breach between Catholic and reformed princes widened, religion became a source of division rather than of unity. Although Luther had never intended to bring about a permanent division within Christianity, his followers gradually created a new church in many of the German states. The Reformation then spread beyond the German states."
If you feel that's the sort of writing that you'd like to follow along with for 1200 pages, then you may as well buy the book, because nothing I can say will ever convince you how evil that paragraph is.
-- update: as I plod along the writing has improved somewhat. that and the immense quantity of information make the book worth reading, though the price is questionable. it's a long book so I might make a more thorough review after another 500 pages.