First and foremost, Little Brother by Cory Doctorow is fantastic story about a young adult growing up in a post 9/11 world full of paranoia, who gets caught up by Homeland Security after a terrorist attack on San Francisco. It paints a bleak view of how much power the authorities could gain if people let them, to monitor all activities and take people with no reason or apologies.
The reluctant hero of the story, Marcus, has a choice after caught wether to lie back and accept the new world order, or fight back. This leads to a fantastic story of someone growing up rather quickly and fighting back against the authorities that wrongly imprisoned him.
The second aspect of this book is the fact that it is open source. Published under a creative commons license the book is available as a free download as well as the more traditional dead tree version. Even better, the downloads page has the story in just about any format you could want, including the standard format for the Sony PRS-505. The author has written up his reasons for offering the book for free, along with suggesting ideas for donations if you enjoy the story.
I thoroughly enjoyed reading this story and have since bought it to pass onto friends and urge others to do the same!