I just finished reading the relatively new book Priests of Mars by Graham McNeill. Published July of 2012, This book is about an explorator fleet of the Adeptus Mechanicus, which is going to go beyond the "Halo Scar" in search of similar fleet that was lost long ago. The object of the original fleet was to find various artifacts of the Golden Age of humanity, which supposedly have the power to terraform dead worlds, drain stars for power, and so on. Various parties are connected to this search, such as a Cadian regiment, Titans, Black Templars, and a Rogue Trader. They are opposed in their quest by a shipful of Eldar, and various elements from within the Mechanicus itself.
The really interesting part of this book for me was the variety of Tech Priests and Magos on parade. You have "brain in many separate jars" guy, and "body given over to combat" guy, and a few recognizably female members too, which is in and of itself interesting as well. This sort of description is useful beyond the confines of this story for those of you interested in making Adeptus Mechanicus armies, or INQ28 skirmish bands. It also reminds you how being press ganged as a serf on a ship would not be the life of adventure that you might expect.
Unfortunately, just as the action is really getting started, the book ends, so one has to wait for the sequel to get anywhere in this story. (the story ends with a few cliff hanger elements as well) Fortunately for me, I got this book from the local library, so did not have to pay $25 for what is ultimately only part of a story. Recommend that you wait for the inevitable omnibus edition, unless you need to read about the various morphology of the Tech Priests.