I keep suggesting all of my friends to read Karen Traviss's Wess'har Wars series, it's easy to read if you already like her Republic Commando tie-ins. A bit difficult if you're not used to science-fiction, military/journalistic descriptions.
The plot (in the main lines) is about aliens disputing a planet, one of them is breeding so fast they need a new planet to pollute and invade, the others are "balancers", they defend nature and all other species without interfering in the environments, they also have super powerful weapons and technologies. Humans enter the picture with their own colonizing projects and the main character, Shan Frankland, is torn between her human fellows with their bad habits (and despising all that is not human), and the Wess'har with Aras, the last of the "balancer soldiers" with a symbiont in his body that made him more or less invincible...
It seems complicated at first, but the more you read and the clearer things get, not like you have to agree with the characters' point of view (there are so many by the way) and it's almost like being part of the adventure, witnessing all of the events with a neutral eye. Traviss is really good at that, too. City of Pearl was some sort of sci-fi revelation to me since I never really read any SF before that. And it made me more aware of ecological matters, and I totally changed my perspective towards other species, animals. I'm reading it again at the moment, while waiting for the 4th sequel
In the same series of novels there are: Crossing the Line, The World Before and upcoming Matriarch in october this year. I can't waaaaitttt