Memory
Memory is an important theme in the novel, since it is what the main character thinks about most of the time. George Bowling is brought back to his childhood (all memories) by many things in life. By the end of the book, he has taken a tour of his hometown, and realizes that almost nothing is the same as it used to be. Deeply saddened that there are no remnants left of his young age, Bowling realizes that they are just memories now, and nothing can bring them to reality again.
Progress
George Bowling, being the main character and protagonist, lives in a time of constant change and what those developers call "Progress". Inspired by memories to visit his hometown, he sees that almost nothing is the same. The pub is still there, as well as the church, but almost nothing else rings a bell. His old home is now a tea parlor, and the beautiful pond where he fished is a garbage pit. Progress, he realizes, is what did all this, and Bowling becomes mad with the world. Exploring what else this terrible force has done, he ponders this question - "Why do things have to change?"