I am very, very late to find this thread, but since The Historian is one of the few books you guys mention on the forum that I have also read, I will give my opinion.  
I remember before buying this book on a whim, my boyfriend once mentioned it to me saying that it was very long and drawn out and he didn't like it at first but later changed his mind. Also, I was very surprised when I discovered what the book was actually about. Anne Rice was my introduction to vampire novels, and the Historian is very far removed from Rice's romantic vampire world. I was pleasantly surprised as The Historian did actually manage to scare me, draw me into the characters' struggle and adventures and weave a very captivating story all at once. In short, I adored this novel. I read Dracula afterwards and found it just a little bit boring, to be honest.