www.authortrade.com claim to put authors together buying and selling each other's books (reviewing as well) and this will raise their numbers on Amazon and other buyers will start buying their books too.

Sounds like another scam that leads right back to the BIG House - Amazon
It is interesting that this program shows up about the time some legal searches are being done regarding questionable UNREPORTED royalty numbers at Amazon, Createspace, and other possible affiliates.

Don't you wish you could represent and sell someone's book and keep ALL the proceeds from the buyer? rl.com/q3spfqt
Cheers, Don