I just finished reading Horror Poster Art (2004) edited by Tony Nourmand and Graham Marsh. I have a great love for movie posters, especially pre-1980s posters. I also love horror movies (as you can tell from the list Dr. M and I have been watching). Combining movie posters and horror movies into one book was a winning combination.
Normound and Marsh broadly define "horror" in their retrospective of movie posters, including movies that could also fit into the categories of suspense or science fiction. The book is nicely produced with beautiful full page shots of posters and well written blurbs about the directors, movies, and artists featured in the book. They also don't limit themselves to US or UK versions of posters, and include many examples from Japan and Eastern Europe. Incidentally, I learned that Poland has the craziest movie poster tradition I have ever seen in my life. Check this collection out -- you will not be disappointed.