Well, Kafka wasn't any better the second time around than he was back in high school.  Still, I found that The Metamorphosis was surprisingly brimming with thematic parallels to World War I literature.  The issue of lost youth and vitality is a huge one in the story, particularly highlighted in the dynamic between Gregor and his father.  Gregor finds himself unable to provide for the family, unable to step up and be the masculine figure of protection and care that he needs to be, and finds himself challenged in this by his father.  As Gregor declines, his father grows stronger; this echoes the confusion in much of the war literature we have read thus far, where the youth die young, fighting the battles of the lingering older generations. 

In addition ,the inability to communicate and function in everyday life was strongly evocative of the lives of PTSD victims, struggling to readjust.  Gregor has, in a sense, adapted to some unspoken stimulus, metamorphosing into an enormous bug, but this adaptation has distanced him from his family.  In the same way, a veteran would return with certain adaptations of behavior and thinking that would clash with the casual, mundane state of everyday life, causing miscommunications, frustration, and possibly violence. 

Stacked on top of all this is the strange obsession with Grete's growing nubility.  The almost incestuous vibe of the story was uncomfortable to read, but it almost seems to reflect the desperation of individuals of the Lost Generation to find and secure a mate.  Gregor's sister is not an ideal mate, yet in a sense she is the only one available to him, because she is the only one who understands him, feeds him, and treats him with some degree of compassion and human decency.  Gregor, however, is of course unable to pursue such a pairing anyways, like Jake from The Sun Also Rises, because he is physically impaired—in this case, a bug. 

I have always found The Metamorphosis deeply disturbing and uncomfortable to read, and while it was an interesting exercise to look at the story from a new angle, it remained a weirdly slimy experience, for lack of a better word to describe it.