I agree with the previous poster, but I would like to add that in addition to the poetry, short stories, and plays that Hughes is best known for, he's also the author of a great number of essays, including his early essay "The Negro Artist and the Racial Mountain." Like many African American artists before and after him, Hughes struggled with what it meant to be an American, a black man, and an artist.
Many of his works seem very optimistic to me, but they also often show that he was acutely aware of racial oppression (as well as other forms of oppression, including class) in the United States in the first half of the twentieth century. Hughes differed from many members of the next generation of black male writers (e.g. Richard Wright and Ralph Ellison) in that he did not often express open protest in his writings. (Some of Hughes' poetry in the 1930s are a clear exception, of course.) Instead, Hughes frequently used humor as both a weapon and a defense ("laughing to keep from crying").