I just finished and a happy to see this thread! I really enjoyed it, I thought that the first half, although it did have a few wordy places, was extremely suspenseful and well done. While the second half moved slower, I enjoyed it also and it was actually kind of nice to be able to relax! I stayed up till three a couple of nights I was so enthralled.
I like the way that he portrayed the women. Obviously he was writing in the romantic period and Laura fulfilled that ideal, but Marian was portrayed the way she was as part of Collins mission of social reform. He wanted to show that women didn't need to be just passive and submissive and that they were capable of much more.
I am now looking forward to reading the Moonstone, I am a detective novel junkie and I have never read it. According to Dorothy Sayers, it is the best of them all (and she is definitely one of the best writers herself, so she should know!)
On a side note, Collins and Dickens were friends and I think it likely that Collins inspired Dickens to try his hand at mystery and that was the genesis of Edwin Drood.
I don't think that Fosco broke his word to Hartwright, and I don't think that Hartwright had a lot of choice but to trust him, also since Fosco was enamoured of Marian that may have influenced him. Incidentally, when Fosco promised Perceval that he wouldn't try and find out his secret he apparently kept that promise also.