I’m seeing positive comments from Jewish as well as Christian sources.
http://www.amazon.com/The-Harbinger-ancient-mystery-Americas/dp/161638610X
Yeah, That is where I started too... ;-)
Here:
http://www.bibleprophecyblog.com/2012/03/book-review-harbinger-by-jonathan-cahn.html#
This is a good review too:
http://modeletics.blogspot.com/2012/06/harbinger-summary_03.html
It is part of a series. They are embedded in the articles linked at the right side, oldest at the bottom of the list for June.