A big congrats to Greek Rural Postmen and Their Cancellation Numbers book. It has won the Diagram prize for oddest book title of the past 30 years:
In The Bookseller's online poll to find the "Diagram of Diagrams", Derek Willan's comprehensive record of a sector of Greece's postal routes gained 13% of the public vote. Gary Leon Hill's People Who Don't Know They're Dead finished second (11% of the public vote) and John Trimmer's guide to avoiding maritime mishaps, How to Avoid Huge Ships (10%) finished third.
A complete list of the books that have won the Bookseller/Diagram Prize for Oddest Title of the Year: Link [wikipedia] (My favorite is The Joy of Chickens).