I am a huge Glen Cook fan. My love for the Black Company series is far beyond irrational, I recommend it to anyone who likes fantasy with an enthusiasm that borders on fanatical. But, as much as I am loathe to admit it, I really just did not like this book. 
 Firstly, one of the very compelling parts of the Black Company is that it is written largely from the perspective of the soldiers on the ground. The Company, if you haven't read the books, is a mercenary band, and they really don't care much for the politics involved in why they are fighting most of the time. By contrast, in this book you are treated to often lengthy genealogies of power that don't really seem to matter. It takes place in the context of a world that strongly resembles a crusades-era catholic church, and the vast plethora of heresies, not to mention the political infighting, create a tapestry of power struggles that, frankly, I had trouble caring about much less keeping track of. 
 Secondly, Cook seems to be attempting an experiment in authorial voice in which every sentence is brief and clipped, and paragraphs are often one or two sentences. It gives the whole thing a fragmented feel that I found off-putting in the extreme. If I hadn't read so much of his previous stuff and known that he is, actually, a good writer, I would have given up on this book three chapters in. As it was, I kept slogging through it out of a sense of faithfulness. I finally did finish it, and the payoff was good, but stylistically the whole thing left me so alienated that I just really couldn't care. 
 If you are already a Cook fan, this is probably worth picking up used just so you can help me figure out what the hell he was thinking. If you're not, skip this and read Black Company instead. I consider Tyranny of the Night to be a failed experiment, and I can only hope it was helpful to him, because it sure wasn't much for me.