In Walter Mosley's White Butterfly, what makes Easy Rawlins' character different from other fictional detective characters such as Dashiell Hammett's Sam Spade, Raymond Chandler's Philip Marlowe, or even Sir Arthur Conan Doyle's Sherlock Holmes?
Sam Spade, Philip Marlowe, and Sherlock Holmes all belong to the ethnic majority in the cities where they practice their trade. That is not the case for Easy Rawlins. Not only is he an outsider because of his dogged persistence at finding out the truth, he is also immediately seen as an outsider due to his race. Because of that, Easy deals with discrimination challenges that none of those other listed detectives deal with.
Another difference between Easy and the other detectives listed is that Easy is an unlicensed detective. He does eventually get his license late in the series, but when the reader is first introduced to him, Easy doesn't have the license. Additionally, Easy does not come from a law enforcement background as do most other "hard boiled" private investigators.