I just finished it, and thought I'd revive this thread.
I enjoyed the book, in the sense that it was never boring, but it is a flawed novel. IMO, the book falls apart halfway through, when Rackham installs Sugar as his daughter's governess. Puh-lease. I know all about the willing suspension of disbelief, but this is just too preposterous, especially when Faber makes such a big deal about presenting a realistic warts-and-all portrait of Victorian London. Especially vexing is when Rackham's neighbor asks him if his new governess is a "Rescue Society" girl--are we supposed to take seriously the notion that women were lifted out of prostitution and placed as governesses? Scullery maids, maybe. A governess was a gentlewoman.
This would be more forgiveable in a novel that didn't pretend to give us a realistic portrait of the time. And speaking of being realistic--Faber relies too much on describing the sh*t in the streets as a way to get us to see what London was really like. There were horses who dropped manure everywhere. We get it. No need to mention it on every other page.
I did like Agnes Rackham--definitely the most interesting character in the book. Faber does a good job of creating someone who's both the epitome of an insipid Victorian lady, and completely deranged.
And Henry Rackham and Emmeline Fox seem to have no purpose in this book. It seems like Emmaline was inserted, simply to let us know that a woman could be respectable and have a sex drive.
I was annoyed with William Rackham. There's really no explanation for his profound personality change. What is Faber trying to say? That a man can either be a free spirit with an overabundance of lust or a captain of industry who's impotent? It's lame to try to get us believe that business worries change him from a horny man-about-town into a boring, staid, stick-in-the-mud.
Edited to add that I'm now reading another historical novel about prostitution--Slammerkin by Emma Donoghue. I'm not finished with it yet, but I'm thinking it's better than "Crimson Petal." Not as bawdy and darker (in 18th century London, a 14 year old girl is forced into prostitution when her family kicks her out of the house), but well written and an interesting historical portrait. It's also based on a true story.