This book was alright; for me it was not as good as any of the Christie Golden books or the War of the Ancients trilogy, but it was about on par with Day of the Dragon/Night of the Dragon. Knaak's books seem very hit or miss to me.
In the end, this book really was just too long (and I am not usually one to whine about length; 500-600 pages or more does not bother me). The nightmares got repetitious and I found myself wanting to flip pages until we were finished with them. The same characters had the same nightmares over and over, and everyone's nightmares were very similar, and we had descriptions of them over and over. As a whole the book was too descriptive, which is a classic Knaak trap it seems. I was bored for the first 200 pages, then it picked up for a little while, and lost me again at the end. It really says something if the climax of the story isn't very exciting. The story could have been wrapped up much more quickly and a lot of extraneous material could have been eliminated. Knaak either needs to watch that tendency in himself or get himself a better editor.
I also didn't really connect with any of the new characters; Eranikus was way too whiney and irritating, and for some reason I couldn't sympathize with him. Others, like Gnarl, weren't around enough for you to get to know them (oh, and he really named the tree-like ancient Gnarl??, come on). Broll and Thura were better, but I still didn't feel all that connected to them. He tried to make Broll sympathetic with his lost daughter etc, but it didn't really do much for me - probably because he really beat it to death by mentioning it every chapter.
SMALL SPOILERS: There were several small details in the wrap up that drove me nuts because they were just way too convenient; Malfurion's and Tyrande's escape from the tree near the end where he just has some lightening strike it is just ridiculous - we have this nearly unbeatable foe, but that is all it takes to get him to drop them? I also found it way too tidy that the the branch was just sitting next to the ax waiting to be used; the Nightmare Lord was really that stupid?
On a more widespread note, he went way over the top with his heroes this time. He has a tendency to make his characters a bit too larger than life (Krasus usually), but Malfurion in this one just went over the top. He's suddenly more powerful than the Dragon Aspects and can do anything at all he sets his mind too, controlling forces all over the world while mentally communicating with friends and rescuing people...yes it is a fantasy book, but this was too much even for fantasy. SPOILER: Likewise, why didn't we get some explanation for Xavius' actions; yes, he's evil, but that is all we get. Why was he hooking up with a "new" patron, and setting out on this new path toward evil. Does he think it will bring him power? Is he out for revenge on Malfurion? Is he being manipulated? All three? We don't know. Knaak spends pages and pages describing essentially the same nightmares over and over, but doesn't devote a single paragraph to explaining why Xavius is doing what he is doing. He somewhat explains how, but not why. I would personally have been happier to see more of that and less of the overly descriptive nightmares.
I did, for whatever reason, like the segment where we see Sylvanas' nightmares; they were much more unique and tailored to the character than the other nightmares and it was interesting to see what still frightens her, which was nice since she tends to be a strong and enigmatic character. If all the nightmares had been utilized in this way to show us the inner thoughts and fears of characters it would have been a lot more interesting, I think. I liked the plot and the story as a whole, I just didn't like the details of it or the writing style utilized, and I felt the characters fell flat, even classic ones like Malfurion and Tyrande. I did like getting to "know" Ysera better, but I wish he would have fleshed out the green dragon flight with a better character than Eranikus. His story for Erankius had a lot of potential, the execution just fell flat.
Essentially this book was a lot longer than it had to be, and took a long time to ramp up and was very anti-climactic and a little too easy to predict. He used too many "easy" outs for the characters and I spent more time thinking "oh really, that really happened that way" than "wow, that was epic" and certainly more than "what will happen next". I may read this again someday to see if I am being unfair, but that will be a while from now. This definitely was not my favorite.