Oh my, I don't think that one star is sufficient to express how bad this book is. There are spoilers below, but I wouldn't worry too much. I would just avoid this horrible book.
The story is essentially a 300-page wagon train running along the Trade Way, with wave after wave of enemies throwing themselves at Shandril, just to be spellfire'd by them. Rinse and repeat. No point to it.
The worst is, they seem to be completely incapable. Powerful wizards with no contingencies, walking in on Shandril without even an invisibility spell, just relying on some very basic plan to grab spellfire and counting on it to succeed, without any backup plan apart from the occasional wand here and there.
Narm is a totally useless character. He doesn't do anything useful apart from whining now and then, and he's completely flat. Not that the other characters have any substance, either.
The tone is also completely wrong. At times, Shandril and Narm are desperate. Other times, they are just having fun while everybody on the wagon train is either killing, dying, or burning stuff.
Then there is the elephant in the room, going all over the whole trilogy: the Malaugrym. They really have no point in the whole story, they seem to have been put there just for show. In this last book, they only appear twice, one at the very beginning, walking in blindly on Shandril and friends to be immediately incinerated by spellfire, and the other just to allow Elminster show off and boss others around.
There's a huge amount of useless mages and priests from various factions, but since they just throw themselves at Shandril inviting her to burn them with spellfire, they are completely irrelevant, when they come up the reader can't remember what faction they were from, and overall it looks just like the old video game Lemmings!, because they go blindly to their deaths.
The only sensible part is when Shandril herself is destroyed by spellfire. The whole book appears to be a very badly-written crescendo leading up to that very point. But then, her reappearance as a ghost, telling Narm to find himself another girl, is the rightly pathetic ending to the saga.
To do justice to the Forgotten Realms and to the author's amazing skill at creating this wonderful world, all copies of the books of this trilogy should be burned, and digital versions permanently deleted.