Jack London is loved because he built his life from zero and many people improve themselves by his novels and his stories. He inspired to people to build, change their life. Our life similar to his life. So We love him.
His book 'John Barleycom' is his autobiography that describes his struggles with alcoholism since youth. He wrote it 3 years before his death (died at 40 from complications of alcoholism). I personally really liked the book because it makes you understand a mind of an alcoholic. I gained a lot of compassion for people suffering this illness of mind. It is probably not appropriate for an abstainer as people complain that the book makes them crave alcohol a lot.
