Written by a Professor of Psychiatry who studied people who said they had encounters with alien beings, this is the outcome of him listening to their stories and taking them seriously.

It's a collection of various stories and regressions of people who claim to have been abducted. 

There's a lot more to this book though, it goes deep psychologically and spiritually.

A must read if you're interested or aware of this phenomena, it's the best one I've read.