Swapship Troopers by Walker Long

A New Kind of War :: A New Kind of Service
During a brutal war against monstrous, spider-like aliens, the Space Marines try to improve morale with a top-secret, gene-splicing drug that temporarily turns men into women. Marines who take the drug have sex with the Marines who don't. Everyone is happier.
Most troopers just blow off steam, but two Marines connect in a way that will change them forever. A young Private gets in touch with his feminine side and finds the joy in submitting to a man. A battle-hardened Lieutenant finds redemption and learns that sexual attraction and respect can go hand-in-hand. How far will this relationship go?
WARNING! This book contains explicit sex, graphic violence, and salty language. It is for mature, adult readers only. [75,000 words]

4 SwapStars

War can harden a man, but the soft touch of a woman can change all that. Women are rare in war. But with the help of PinkVector any man can be transformed into a woman in every sense. 

While off fighting BUGS, the men get a little break. PinkVector is injected in several males. Q is injected and becomes a gorgeous woman, that any man would be lucky to have. Hardaway keeps Q for himself. It is thru the fighting and killing, that a love story emerges between Q and Hardaway. Q realizes that he enjoys being a woman and never turns back. 

This is an action packed story with a tweak of romance sprinkled in. I loved the action parts, but I was held captive by the romance of the story. It seemed odd at first that men would willingly take PinkVector and take their turn. Kudos to Author Walker Long for using his imagination and coming up with something like that. Brilliant and inventive. I enjoyed the store, the last 10% of the book I was worried and on the edge of my seat trying to figure out if there would be an HEA or a death scene!!! Frustrating! All in all a good read that will have you wondering what the future holds.