The most annoying thing about the book is the habit most of the characters have of bursting into song or reciting poetry without the slightest provocation. The second most annoying thing is the unbelievable verbosity of style - the river Don is described as "lutulent" when Turpin crosses it, and I have no idea what that word means. (NB this is the river Don of Doncaster rather than Aberdeen, Toronto or Rostov-na-Donu.)
Ainsworth says in his introduction that he wanted to write a Mrs Radcliffe novel; I haven't read any of those, though I did rather bounce off Northanger Abbey which was a send-up of the genre. I was struck by the uneasy handling of heroism, virtue and social order. It begins with young Peter Bradley discovering that he is really the heir to the Rookwood estate, and appparently being set up as the hero; but he slips rather casually into the role of villain as the book progresses, without any decent signalling of the transition. The gypsies are individually quaint but collectively sinister. Ainsworth wants Turpin and the highwaymen to be heroes, and his pursuers buffoons, but can't quite deliver. The book's one memorable line is when Turpin and friends are drinking in a London tavern just before the ride to York. Turpin proclaims, "May each of us meet with the success he deserves," to which one of his fellow-highwaymen replies, "Egad! I hope not! I'm afraid, in that case, the chances would be against us."
My actual reason for reading Rookwood is that it appears in Jacqueline Rayner's Doctor Who audio play, The Doomwood Curse, in which the Sixth Doctor and Charley Pollard are drawn into a world which seems to be based on Ainsworth's novel - particularly recommended because of India Fisher's bravura performance, and you don't need to know anything at all about Rookwood to enjoy the play.
This has been my Blackberry ebook for several months, and a wonderful cure for insomnia in the small hours. I now have the contents of the Hugo Voter Package to replace it in the former category, but I hope not in the latter.