with David Brin's Uplift universe and add a dash of Ender's Game for good measure? Why, Old Man's War, the latest novel that I managed to finish during my extended bout with strep throat!
Old Man's War is the premiere novel by John Scalzi, a new talent (at least at the time this was published in 2005), with owes a heavy debt to other military SF (e.g. Starship Troopers by Robert Heinlein, The Forever War by Joe Haldeman). It was nominated for a Hugo award for best novel in 2006.
The novel tells the story of John Perry, who at 75 years of age, enlists in the Colonial Defense Force (CDF). Like all recruits, in exchange for his service, he is given a new genetically-modified, youthful body, and, upon retirement, the freedom to settle on a colony off Earth. The first half of the book details his training and initial combat experiences. The second half really gets to the meat of the plot--the CDF finds itself in conflict with an alien species over Coral, one of the all-too-few planets in the galaxy appropriate for colonization. The Rraey have gotten a hold of technology which allows them to predict where CDF ships will materialize (see Skip Drive below) when they launch a counterattack to take back Coral. As a result, the CDF fleet is annihilated, and Perry is the only survivor. He is rescued from Coral by a company of soldiers from the Ghost Brigade, the special ops branch of the CDF. Perry is attached to this special force for the remainder of operations on Coral, and comes to some interesting realizations about himself in the process.
Interesting technology abounds in the book--while none of the concepts are particularly novel to SF, they are seamlessly integrated into the world without being gratuitous. Genetic engineering and consciousness transfer are essential for the creation of CDF troops. Each recruit is interfaced with a BrainPal that allows people to communicate images, sounds, thoughts, etc. with one another--this is critical to the efficiency of CDF forces in combat. FTL travel is made possible by the Skip Drive, which essentially works by punching a hole in the fabric of the current universe through to another highly similar universe.
While I found the novel to be both interesting and entertaining, I kept coming back to one major issue: the CDF lacked a really compelling adversary. They spent most of their time running around the galaxy fighting sporadic turf wars on any given colonial planet against any given alien race. I would have found the plot to be more compelling and had a more substantial connection with the characters if the CDF was fighting an avowed enemy of the human race. Something similar to the buggers in Ender's Game or the arachnids in Starship Troopers. By the end of the book, we did have a reason to disdain the Rraey, but it took three-quarters of the book to get to that point. Also, there was a large disconnect between the CDF fighters and the colonists they were defending such that the CDF seemed to have little reason to care them (other than the fact that they were human, which I suppose be a profound motivator in the depths of space), and, consequently, neither did I.
Overall though, an extremely entertaining read. I'm looking forward to reading the sequels (of which there are currently three)!