Yes, by that definition, Dracula: The Un-Dead is a sequel. But having read the original and this work back-to-back, really highlighted the classic nature of the original, and the commonness of the follow-up.
se⋅quel /ˈsikwəl/ –noun
1. a literary work, movie, etc., that is complete in itself but continues the narrative of a preceding work.
2. an event or circumstance following something; subsequent course of affairs.
3. a result, consequence, or inference.
Origin: 1375–1425; late ME sequel(e) < L sequēla what follows, equiv. to sequ(ī) to follow + -ēla n. suffix
The original novel is suspenseful, lyric, haunting, surprising, subtle and thoughtful. This book is obvious, grotesque, and desperately begging for a film option.
I will admit, from a personal point of view, Quincey Harker's and his mentor's relationship held my interest in the opening chapters, and there were aspects of the period represented which were detailed and interesting. However, once the action begins moving, it's all very trite and spelled out in broad terms, the broadest of which is the villain, Countess Bathory, who is a very irritating character. Painted as a man-hating, drag-king, lesbian-witch from Hell, she is quite simply boring in every scene she is in.
My question is, my not take the risk and create a sequel that is written like the original, in found letters and documents? That simple (yet difficult) conceit makes the story live in the moment - and makes the mystery that much more mysterious, as we live the tale through those who do not know everything. Dracula, as presented in Bram Stoker's novel, is a complete cypher, he speaks for sure, but we only hear his thoughts through others. As penned by Ian Holt (and fronted by Dacre Stoker) he and Bathory are too accessible - in his case, far too much like Lestat or other vampires who have come since, and that brings this legendary creature far too close to earth.
Why so much time spent on a review for a book I disliked? Because I felt compelled to finish it because of this play, otherwise I would have returned it to the library two weeks ago. I do not have time to read any more vampire fiction, it's 2010 and I need to get me a biography of Jesse Owens.