In cities with weekly rep, and in towns that were visited by touring companies (remember, even tiny towns had an Opry House) people went to the theater the way they used to go to the movies, more or less irrespective of what was playing, and the way people now flip the channels or DVR equivalent. So a) there was a huge demand for almost ANY kind of entertainment, and b) before international copyright there was a tremendous incentive to turn books from other countries into plays. And of course Dickens was constantly bedeviled by extremely unauthorized adaptations--sometimes before he even finished the novel in question. And of course the Tom Show is a genre of its own. Do you remember Nicholas Nickleby's gig with the Crummles Theatrical Co? His first assignment was to plagiarize a French play the Crummles had a copy of, but with the addition of the two tubs and a pump that the company had recently acquired and needed to amortize.

There is a whole *book* about the Balderston version of Dracula, although I can't remember the author or exact title--but David Skal wrote a bunch about the play. In an actor-manager company, Dracula was probably played by the boss!--otherwise, the Heavy Man. BTW when Paul Darrow (B7's Avon) was in weekly rep, he played Dracula at least once.

If you ever want a readable quick guide to Everything You Need to Know About Victorian Theatre, Robertson Davies was a big fan-- try The Mirror of Nature.