John Scalzi. A very fast hard sci-fi read. Humans are colonizing the galaxy, in competition with hundreds of other species. The seemingly universally violent contact between species is carried out by soldiers who are largely retirees who have been given new bodies. Not bad in terms of characterization and interesting relationships, but a big thumbs down on the simplistic treatment of what to expect from aliens and the reliance on preemptive violence.
Kenneth Sutton's aide-mémoire