What can you tell about Kreb's goals and aspirations from the way he spends his time?

While Krebs was abroad serving in WW1, his previous childhood experiences and days at a Methodist college were swept away by violence and horror. His indifference to goals and aspirations reflect his emotional and spiritual numbness. Meanwhile, the world he left has barely changed, or only changed superficially, and Krebs can't gain traction in trying to fit in -- if he even cares to. His lethargy is considered unproductive and immoral by his mother, who just wants him to get a job and wed. He declines. He lacks physical and emotional energy to pursue employment or love. Krebs has worn out his welcome with friends and family, who have heard all his inflated war stories and expect him to get along. Now he hardly speaks to anyone. Today's readers may consider that Krebs suffers from PTSD or is shell- shocked. But his inertia is far more complex.

As the story opens, the narrator describes Krebs' routine:

...he was sleeping late in bed, getting up to walk down town to the library to get a book, eating lunch at home, reading on the front porch until he became bored and then walking down through the town to spend the hottest hours of the day in the cool dark of the pool room.

On a day-to-day basis, it is fair to say that Krebs' existence consists of killing time. He is not being productive, nor is he attempting to reintegrate into small town, Oklahoma society. His goals and aspirations might be to simply avoid challenging himself physically, intellectually, or socially. Hemingway's narrator implies that Krebs has been so psychologically damaged by his war experiences that he is now adrift, rejecting the beliefs and values of the people who surround him.
However, Krebs enjoys reading books about the war. It seems that he wants to understand the political forces that created it and the big picture of how it was fought, something that he could not concern himself with while on the front. His goal might then be to come to terms with what WWI meant to the world and the meaning his own role carried.