In the African American genre there is such heavyweights as "Mosquito" by Gayl Jones, "Roots" by Alex Haley or "Palace Council" by Stephen Carter and much more.
But there are heavyweight readers for heavyweight novels. Some people take long novels in their stride. They enjoy characters that are extremely well developed, relish the enduring plots that twist and turn, and savor those massive novels or non-fiction books that offer so much background.
I belong to a Book club and have been a member for 2 years now. Each person is recruited to select the book for the month and host the discussion on the book of their chosen. For the month of September, 2009 the biggest book I may ever read was selected....there goes my summer reading. "Ida: a sword among Lions" was the chosen book. A massive (800 pages) this book is a heavyweight contender for the title of longest novel. Although it's not a novel but an autobiography of Ida B. Wells, also known as Ida B. Wells-Barnett, who was an African American civil rights advocate and an early women's rights advocate active in the Woman Suffrage Movement. Fearless in her opposition to lynchings, Wells documented hundreds of these atrocities.