Full review with other Palace of the Vampire Queen related material here: http://theotherside.timsbrannan.com/2020/01/classic-adventures-revisited-palace-of.html
The first sequel to Palace of the Vampire Queen is Castle Blood. Now here we get more modern adventure designs and maps. There is more background here too to hook the players in,
The adventure is brief, but it is supposed to be, at just 16 pages. It can be run in an afternoon. I actually felt this worked better as a prequel to the PotVQ. You learn more about her history here. The eponymous castle is all detailed and above ground. You can meet the Vampire Queen here, but killing her is not the goal of this adventure, but rather finding out what is going on.
A fun adventure that is easily adapted to a wide variety of games.