Upton Sinclair had socialist political opinions. Most of Sinclair's books, including The Jungle, dealt with social injustice. He also wrote a book called Mental Radio where he claimed to have conducted telepathic experiments with his wife.
He wrote many other books. His book The Flivver King was about the Ford Motor Company. The Flivver King was written at the time when workers at Ford factories were trying to start a labor union. He wrote a series (many books in a row) with Lanny Budd as the main character. There were eleven (11) Lanny Budd books. The Lanny Budd books were about current events in the World at the time.
He later joined the Democratic Party and ran for governor of the state of California in 1934. He wanted California to start new businesses which would be run by the state government. This was to help people who were unemployed (did not have jobs) because of the Great Depression. He lost the election.
He retired in the town of Buckeye, Arizona.