If the beginning holds up, the story of the life and military operations of the hero (2/3 of the book) can be convincing, the author clearly does not know it. One has the impression, reading, watching a bad action film series B, where scenes more and more ridiculous and absurd succeed and lead you to a bombastic and ridiculous apotheosis.
When the "coup de theater" of the novel, the famous "special forces", it falls like a cheese soufflé: not only is it easy to guess what they are, right from the beginning of the story, but they n 'nothing so special after all.
In short, if you want to read a good novel in the same genre, buy The Forever War Starship or tropes (stars, to guard you in French), but not Old man's war!
Enjoy reading