Coming as no surprise, this book is pathetically bad. Although this is not unusual with Salvatore's books, this whole series appears to be insufferable.
Theoretically, this book follows the story of Cadderly while he comes to evolving into a more mature cleric and a Chosen of Deneir, becoming aware of the powers that come along with this stature. In the meantime, he and his friends face another threat from the renowned band of assassins from Westgate, the Night Masks, and in particular by a master assassin named Ghost who is able to exchange himself with other people.
This synopsis might well do for a very good book. Unfortunately, it turns out childish and stupid.
Let's start with the plot as a whole. Like most of Salvatore's books, this one contains a very definite distinction between good and evil, so naive that not maybe only as a child I would have believed it possible. Basically, the bad guys, when they are not being ruthlessly killed, always wear some sort of wicked grin on their face. You might well imagine the good guys painted blue and the bad guys painted red, for all the subtlety of the plot.
Again like most of Salvatore's books, in the end the good guys come out basically unscathed. Yes, Headmaster Avery is dead, but he was essentially a very minor character from the beginning of the series. However, in other books, at least the MCs face some difficulties at some time, some temporary setback that they eventually overcome. Even in In Sylvan Shadows, Cadderly,Danica and Elbereth are captured and their fate is temporarily at stake. That gives at least a minor sense of suspense.
In this book there's no such thing. Every time the Night Masks attack, the whole fight goes always perfectly smooth for the MCs. No wound is ever serious, Cadderly gets exhausted by Deneir's song but that exhaustion never has any significant side effects, and so on. At a point, it seems to get just a very little interesting when Pikel is controlled by Ghost, but even that attempt is thwarted in the next page or so. There is not even the slightest momentary accident for the MCs. This makes the plot so boring and completely devoid of tension. Not to mention that a huge amount of unfavorable situations is solved by lucky strokes, a.k.a. deus ex machina.
The Night Masks are supposedly a formidable band of assassins, but if I should draw any conclusion from this book, they would basically look like the bad guys in a Bud Spencer movie. They attack in waves, but they are constantly and easily beaten by the MCs. Not that their attacks are particularly effective. Rather than a band of assassins, they look like a lowly band of brigands. For example, why would a band of formidable assassins attack two people on a boat using attacks on the water, where they are clearly visible? Or why would a formidable assassin with a crossbow leveled on Ivan take the time to wickedly greet his target, and take so much time as to allow Pikel to break the support for the chandelier (it takes some time, according to the text) and let it fall on himself? That's no fantasy, that's Hanna & Barbera.
Speaking of crossbows, there is not a single bolt from the Night Masks that scores a hit, so they are also very pathetic with weapons. Needless to say, when Danica takes a crossbow, she doesn't miss a single hit.
Ghost is the most ridiculous villain I have seen in a book. I understand that Robin Hobb hadn't yet written her books at the time of this one, but Salvatore could do something definitely less dumb than Ghost. He is described as an artist, a master, and he is completely ineffectual. First, he always acts in a very suspicious way, so that when Cadderly or, later, Ivan sees him, they immediately realize that he is up to something, and that already disqualifies him as a good assassin. Second, he procrastinates his kill very long (no reason explained, but it is clearly stated that he had had several occasions to kill Cadderly). Third, he makes plans that never take problems into account, and in the end all he does is improvise. Seriously, one would think that his targets have always been just much more inept than he is, which is already a lot. If he is an artist, then he must be along the line of Jackson Pollock.
As for the characters, they are totally stereotyped. Cadderly turns from a self-effacing person, who somehow manages to get by (which was not so bad) to a know-it-all who now has a ready solution for any inconvenience. He also has very unconvincing and selective conscience issues, more or less according to the convenience to the story. As much as a "Gary Stu" can go, I'd say. Danica is basically nothing else than her fighting prowess. The dwarves are the most annoying comic sidekicks ever, they are essentially the most basic essence of the brutal dwarf, something along the line of "kill me enemies, help me friends, get some food". Furthermore, they're supposed to be funny, but they're not if you're anything above preschool (a ridiculous example: the reference to Pikel's "amelly dwarf toes". But Pikel never wears anything other than sandals, so his toes should be no more smelly than, say, his elbows. The reference to the smelly toes is just childish, like children that say that toes smell even when they don't). I assume that Salvatore had a son or daughter in preschool while writing this book. Ghost is nothing more than the evil guy who only wants to do evil things for no particular reason (his POV parts do not say anything about his motives, other than he is an "artist"), and Bogo Rath is… well, I don't even understand what was the point of including him in the plot. No significant introspection anywhere. The only character that offers a bit of interest is actually Kierkan Rufo, who is a weakling who does evil things only because he is unable to keep control of himself.