Joe Haldeman 
Forever War #5 [PDF ebook] 

The interminable waiting continues as Mandella treks across the void to his next assignment. Alone now, with Marygay light years away, forever out of reach, he has only memories of the life he once knew.Among his comrades and subordinates, he finds he is an oddity, as humanity has developed new social constructs beyond his comprehension. Some things, however, remain the same, and Mandella finds himself at the center of an outburst of the basest human emotions.