Complex sentence: Although character names have been changed, the protagonist is named Oscar Devereaux, and the main theme of the book is that African Americans can realize their potential and succeed in areas in which they may have been previously denied access.
Split into simpler sentences: Although character names have been changed, the protagonist is named Oscar Devereaux. His theme was about African Americans' realizing their potential and succeeding in areas in which they may have been previously denied access.