Storyline: 4/5 
 Characters: 2/5 
 Writing Style: 3/5 
 World: 5/5 
 --Below information added approximately a year after original reading-- 
 I made the mistake of reading this shortly after finishing the Forever War by Joe Haldeman. To keep them distinct, I should have read them far apart from one another. The Forever War, after all, preceded Old Man's War by over 30 years. Generations of new writers had come, published, and moved science fiction along in that time. The two works do bear surface similarities: both are space opera with heavy emphasis on the military with time split between Earth and the heavens. Haldeman's book, however, was much more somber, grittier, and sociological. Scalzi's, by contrast, was bright, humorous, and technologically inventive. 
 Old Man's War falls into that category, which I commonly note and enjoy, of idea books. It puts forth something ingenious and exciting, something truly novel, and then it lets it loose to see where it goes. Scalzi rewarded the reader with a good setup and sense of mystery. Once the main idea was revealed, however, the rest of the book was somewhat dull in comparison. Scalzi keeps the reader interested with adrenaline and some witty dialogue, but by the halfway point, you have to realize that the best is already behind you. 
 A good idea goes a long way with me. I can certainly see how someone with different tastes and standards would judge this much more critically.