I decided to read the book after seeing the film last week. Both have the same premise but they are different in treatment and ending, in a way I prefer the Japanese version. It could easily have been presented in a graphic novel format (which exists) than the prose it was written in.
I have a little issue about time travel and the mechanism of it because, in all the novels I've read, it was never explained to my satisfaction. It can't be with a 230 pages book so I decided to suspend disbelief and concentrate on the character's struggle and interactions.
So this story is a take on the old Groundhog Day movie where you wake up and re-lives the same 24hrs over and over again. Keiji Kiriya does a rince and repeat of his first day as a soldier on the muddy battlefields of Japan and learns something each time he goes through the loop.
Mimic are alien invaders trying to exterminate mankind for a good 20 years. The army always needs fresh meat so Keiji goes on a little island near the coast of Japan on his first battle with the enemy. He is scared shitless and gets killed right as the battle starts...to wake-up in army base 30 hours before the strike. He quickly realizes that he's trapped in a time loop but no matter what he does...he still ends up on the battlefield and dies. Again and again.
One of the interesting part of the story is all the little things, how he decides to shave off time on his unending routine to train his body and brain. The only thing he can take forward is his memory so the body stays the same, he does not build muscle. There is an old samurai principle mentioned in the book: ‘Kiri-oboeru’ which roughly means strike down your enemy and learn. This completely disappear in the movie but it's the focal point of even the name of the book. How he learn to appreciate his comrades in arm and his commanding officer that he originally hated...even if everybody else experience his day for the first time and don't share the deeper connections he makes. How excellent food becomes awful after 100 repetition...
In all Keiji's struggle there is one constant: an American female soldier named Rita Vrataski. She has more Mimic confirmed kills than anyone on the world and is known as the Full Metal Bitch. Funnily enough, none of the main characters are even remotely close to the movie actors....well maybe the action figures described in the story are a very close match (yes, they made a movie about Rita in the story and action figures, it's a Japanese novel after all).
Another point in it's favor (and because I've read too many american novels lately) is that ending is bittersweet. If you like video games and first person shooter....you might appreciate the irony of this book.