The Ultimate Hitchhiker's Guide to the Galaxy eBook: Douglas Adams, Neil Gaiman: Kindle Store for $11.99 + free shipping
This is my favorite 5-book trilogy of all time: The Hitchhikers Guide to the Galaxy, The Restaurant at the end of the Universe, Life, the Universe and Everything, So Long and Thanks for all the Fish, and Mostly Harmless. "The Ultimate" contains all 5 books plus a bonus "Young Zaphod Plays it Safe".
This is the Kindle Edition. Normally I stay away from Kindle books over $9.99, but am justifying this one at an average price of $2.40/book.