Dracula, by Bram Stoker (with illustrations by Edward Gorey), text originally published in 1897, illustrations in 1979.
My edition of Dracula is decorated with illustrations by Edward Gorey, which is exactly why I bought that particular edition. The illustrations came from Dracula's Toy Theatre.
I remember not being able to finish this book the first time I tried to read it -- I was that caught up in it and terrified. Finally, I read it completely some time in my 20s, before the painful Gary Oldham movie version was released. And now, about twenty years later, I've re-read it. Bram Stoker wasn't a brilliant wordsmith, but he knew how to tell an incredibly dramatic, suspenseful, and rather ghastly tale.