This was an impulse choice for me at the local B&N. Sean Williams other works with Sean Dix haven't ever done very much for me. But this one, it was interesting.
Its a murder mystery - one trying to solve a murder approximately 200 millennia old though. This is an interstellar setting, but one where light speed is the absoloute limit and mankind has reached throughout the galaxy and diversified in many, many ways. In some ways its like Alastair Reynolds Revelation Space series, but not quite. One major difference is the way humans characterize themselves - singelton (single ID, capable of gestalt), Prime (old style human) and fort. The dominant form of mankind are the forts, gestalt humans that have slowed their time sense to a galactic scale (yet are still able to interact with and beat normal or accelerated humans (I know I had a hard time with it too)).
In Saturn Returns, Imre Bergamasc gets his old unit the Corps back together after being reconstructed from a partially destroyed recording beyond the galaxy's rim to determine who killed him. Along the way we get a decent look at the Mandala supersystem (which would make a great hard SF game setting BTW).
It's interesting, it deals with identity, what it is and what makes a person - memory, experience, time sense, etc. For that its interesting and worth checking out the expected sequel (the ending opens it up with Earth as a destination). But, I think Williams needs to work a little more on explaining his setting somewhere and perhaps firming up his neuroscience.