Ravenloft II: The House on Gryphon Hill was the much awaited sequel to Ravenloft. Ravenloft II was I10 in the "I" series of AD&D modules (first edition rules), it contained 48 pages (not including maps). Released in 1986, it was aimed at levels 8-10. Just like the first Ravenloft, it was written by Tracy Hickman and Laura Hickman and illustrated by Clyde Caldwell. It is based in the domain of Mordent (back when it was just Mordenshire).
Ravenloft II seemed a bit out of focus. Whereas Ravenloft put a plot around a dungeon crawl to make it something more, Ravenloft II started out with a story format. Without wanting to give away the plot, you get to meet more of the BIG NAME people in the sequel than in the original Ravenloft. That feels a bit overwhelming when reading through it, so I'm not sure how it would play out in an actual game.
Unfortunately, I've never had the chance to put a party through the adventure, but perhaps I might be able to now, since it's available on the Wizards of the Coast website for free download. ( http://www.wizards.com/dnd/files/RL2/RL2.zip )