Also a personal note: I read this a couple of times in the 1960s. The second time was for a high school English class. I was overjoyed: after the tedium of Dickens and Flaubert, here at last was a fun read, and one I'd read already. Easy peasy!
As it turned out I got lousy Hound-related grades. Reading for fun is not the same as reading for school. Don't get them confused, kids!
Anyway: Holmes and Watson are drawn to the mysterious case of the Baskerville noble family, which seem to have a long-running problem with a monstrous supernatural dog. In the 1700s, it allegedly did in Hugo Baskerville. And now it seems to have returned: the body of Sir Charles Baskerville was recently discovered outside the manor. Next to him were footprints. And, guess what:
"Mr. Holmes, they were the footprints of a gigantic hound!"
Next in line: Sir Henry Baskerville, recently arrived from North America. Holmes and Watson decide to take the case, and (hopefully) save Sir Henry from almost-certain doggy doom.
I see that Season 2, Episode 2 of the BBC's Sherlock is titled "The Hounds of Baskerville". Scheduled for May 13 American broadcast, and I am so there.