I recently came across a site offering free book downloads and several of my cozy mysteries were listed without my permission. They have a form for copyright complaints but when it's filled out it doesn't accept the information. Response to a Cease and desist E-Mail was "the matter will be dealt within 24 hours", but to no avail. The copyright office suggested I contact the FBI (they have a form on their site). I also found out from a contact at Chickensoup for the Soul that they have been trying to get this site taken down for years and rather than free books, all you will receive when trying to download is a virus.
The best advice - if it seems too good to be true, it usually isn't worth the risk.
Note: The only free books offered by me are through Amazon, or Smashwords.com with a coupon