Hybrids is the final book in the Neanderthal Parallax trilogy by Robert J. Sawyer.  It's a great wrap up to the whole story, but I have to admit, I'm having trouble identifying what this particular book is about.  The theme of "Playing God" stands out, and fits with the overall religious theme but the book itself is really just a continuation of book two.  In other words, it couldn't really stand on it's own.  But that's fine.  There's no rule that says each book in a series has to be a complete story.  I just think it's better when it is.  

I can't really describe much, lest I give away details for the first two books, so let's focus on what I can say.  Homo Sapien humanity now has access to Neanderthal technology.  Their technology is much farther ahead than our own in many ways (while ours is ahead in others).  What will we do with that power?  What will we do with access to an unsullied copy of Earth - a veritable Eden?  What wouldn't we do?

As a side story, the Earth (our Earth) is going through a magnetic collapse, or excursion.  This happens often enough to varying degrees, but rarely on a planetary scale.  It has happened once while Homo Sapiens walked the surface.  We call it the Laschamp event, and It coincided with the supposed dawn of consciousness 40,000 years ago, also known as The Human Revolution.  Since magnetic signals can have an effect on the human brain (see the God Helmet), what will be the effect this time?

The Good: Still great writing.  Well researched.  Keeps you guessing right to the end what's going to happen, and even more importantly, why.
The Bad: Not a self contained book.  You can't just jump in.  You must read books 1 and 2 prior to this.
The Ugly: Once again, nothing to put here.

It's a great trilogy, and an interesting look at the soul of humanity.

Links of Relevant Scientific Interest:
http://en.wikipedia.org/wiki/The_Human_Revolution_(human_origins)
http://en.wikipedia.org/wiki/Geomagnetic_excursion
http://en.wikipedia.org/wiki/Geomagnetic_reversal
http://en.wikipedia.org/wiki/God_helmet