When I was young I used to think that Jack London was a children's author, who wrote books like watership down, but set in the US. At some stage I did read John Barleycorn, a book about his drinking life. There were some great scenes in this book, like when some hard man bought him 3 or 3 drinks, before he understood "the round system".
After that I read The iron Heel. This was a political book. As the article in the inddependent notes, his politics was socialist, but some times a bit confused. I did read that Emma Goldman complained about that he talked socalism, but he never did anything.