I'm reading the book A Man Called Intrepid by William Stevenson, and it's claiming that Hitler lived in Liverpool before world war one. I also found a guardian page making the same claim. Is there any truth to this? http://www.theguardian.com/notesandqueries/query/0,5753,-1915,00.html
No, there is no truth to this claim. It is only speculation.
Hitler never lived outside of Austria (his native country) or Germany (where to moved to at age 23/24, just before the outbreak of World War I). And that has been confirmed. In fact, Hitler never visited England.
If you would like to read a very good biography of Hitler, with confirmed sources (and not useless speculation), then I would recommend Joachim Fest's book.