I love to have dinner parties, and have always wanted to do a murder mystery dinner party.
I went looking and unfortunately our library system doesn't have a book on how to host such a party. It seems that there is not a readily available book, and most of the products sold are kits with a ready made script, props, and accessories provided. Buying a kit is probably the easiest thing to do, but Susan Haley-Zemanek had a good article on her blog , detailing how to write and create your own murder mystery! Another article by Donna Pilato on About.com gave tips  on hosting the party. Don't know when I'll get the time, but it sounds like a fun project!