Better yet, read them both. John Scalzi's "Old Man's War" and "The Ghost Brigades" are great science fiction stories, and I recommend them both. I also found the personalization of the main characters to be great - I really wanted to know what was happening with them, and not only laughed out loud but wept as the stories progressed. "Ghost Brigades" isn't exactly a sequel to "Old Man's War"; it's in the same universe, with some of the same characters, but you could read either as a stand-alone. I hope more stories about the Colonial Defense Force are on the way!
Check 'em out from your local library. And a thanks to my husband's boss, who loaned him "Old Man's War" in the first place - I'll be adding both to our home library.
Currently a balmy 95°.