Silverfall is perhaps a typical example of why RPG tie-in novels rarely work. Greenwood is the lead designer of the Forgotten Realms setting, and deserves a lot of respect for that, but fascinating setting characters like the Seven Sisters don't necessarily make for interesting protagonists in a novel.
All seven are too much like a masochistic RPG geek's wet dream to be truly memorable: extremely powerful and magic-savvy, tall, beautiful, mysterious, but at the same time a bit slutty and accessible even. The adventures they have, all involving saving the Realms from a plot hatched by the dark goddess Shar in a sort of relay race where one sister takes over from another, are entertaining enough, but frankly, it's more fun playing such a thing than reading about it, especially when you can see D&D game mechanics shine through just about every paragraph.
There are pleasant exceptions to the above observation about RPG novels, but this isn't one of them. Only for total Forgotten Realms freaks and completists, this one.