It is interesting to note how many people, after reading the reviews, came to this as fans of his contemporary mega series "A Song of Ice and Fire". Many were disappointed because this is so different. One reviewer decried that this novel was far too short. Perhaps some people were put off by there being a mere two strands to the narrative (compared to ASoIaF's Sixtyfour)?
The only other Martin book I've read was "Game of Thrones". I quite enjoyed it but not enough to make me want to embark on another never ending monalith of a series. That series is just too long. The individual books of which it comprises are too long. But I guess that's innevitable given the large number of narrative strands (sixtyfour was a guess by the way). The plot would barely develop from book to book otherwise. But that doesn't make "Fevre Dream" too short. This is a novel, not a soap opera. Four hundred pages is plenty for a novel. The only time I would say that a novel is too short is when it feels rushed. This doesn't. It runs at a leisurely (river boat) pace, progresses nicely and concludes satisfactorily. If you want an endless progression of character interactions that doesn't have a logical beginning nor resolves itself, look elsewhere. There are plenty of never ending soap opera/fantasy series out there.
Another reason that might put off the modern reader is: vampires. Yeah, ok, we aren't exactly short on vampire stories these days. This was written decades ago and you can't really fault it for that. But rest assured (or be warned), there is no paranormal romance to be had here. Again, if that's what you are looking for, you won't have to look far to fill your boots these days.
So what we have is a great story in a great setting (well, if you like the idea of riverboats on the mississippi in the 1850's). I felt there were some vague simularities with Anne Rice's "Interview with a Vampire" and if you liked that book, you should like this. I've not read that many vampire novels but this book presents an interesting take on the myth that hasn't been done in quite the same way before (as far as I know).
A worthy addition to the Fantasy Masterworks series that is quite dark in places but doesn't quite stray into the realm of horror.