The novels of writer Jack London are typically somewhat autobiographical, so you could say they are loosely based upon his life. He is best known for books that center around a character in a struggle against nature, but there are also a great many buried themes and messages within his books.
While part of what Jack London's novels are based upon is his life, there are also some themes that could arguably form the basis of many of London's works. Typically London's writings contained themes of:
Jack London was born in 1876, and began life as a sailor at the tender age of fourteen. He cruised most of the world this way and eventually landed back in California in the wave of the gold prospectors. He settled into a home there and began to write about some of the things he'd experienced and learned on his journeys.
Jack London wrote many short stories, which were loved by critics and usually devoured by readers. He used his experiences around the world to write about struggles of humans against the brutalities of nature.
His series of short stories about life in the Yukon were collected into a book called Son of the Wolf, published in 1900. His best known book was published three years later: Call of the Wild. This is still the one most often associated with his name; it tells the story of an Alaskan dog striking out from a civilized life to join a wolf pack.
It can also be argued that part of what London's novels were based on was theories of evolution. A serious believer and scholar of Charles Darwin's theories of evolution, London considered survival of the fittest to be at the core of everything he wrote about - and, indeed, at the core of most situations in life.
He was also a political philosopher, and had a deep passion for social theories that shaped the way that people lived in conjunction with one another, removing them further and further from a natural state of being. London believed in the theories of Karl Marx, and this can be seen in some of his earlier writings in a subtle way. He writes severe criticisms tinged with horror describing the slums of London and predicting a revolution of the people.
London believed in a return to the land as the solution of many of our problems. The central conflict of man against the surrounding environment was, to him, the essence of existence, and he had strong beliefs against any societal organization that took humans further away from that by interfering with the natural pace of their lives.
This can be seen again and again in his novels, each of which, in its own way, tells the story of a person - or animal - returning to his roots within the natural earth in order to restore sense and rhythm to life.
These major themes, therefore, were all things that Jack London's novels were based and built upon.