Home Fires — Gene Wolfe

Gene Wolfe takes us to a future North America at once familiar and utterly strange. A young man and woman, Skip and Chelle, fall in love in college and marry, but she is enlisted in the military, there is a war on, and she must serve her tour of duty before they can settle down. But the military is fighting a war with aliens in distant solar systems, and her months in the service will be years in relative time on Earth. Chelle returns to recuperate from severe injuries, after months of service, still a young woman but not necessarily the same person -- while Skip is in his forties and a wealthy businessman, but eager for her return.

Still in love (somewhat to his surprise and delight), they go on a Caribbean cruise to resume their marriage. Their vacation rapidly becomes a complex series of challenges, not the least of which are spies, aliens, and battles with pirates who capture the ship for ransom. There is no writer in SF like Gene Wolfe and no SF novel like Home Fires.