This is an interesting book. Actually, it's more about sociology and folklore than a mere collection of dirty jokes.
Basically, the white folklorist Roger Abrahms spent some time in the late 1950s living in the Philadelphia ghetto. He befriends a number of the locals who are fascinated with his tape recorder (this was when they were new) and proceeded to record their folktales, songs, rhymes, and stories.
To his credit, Abrahms does not patronize his black sources. He also writes about them and their lives with respect in the chapters preceding the tales. But what makes this controversial is that the tales he records are the rough, uncensored kind that black comedians like Redd Foxx, Rudy Ray Moore, and Richard Pryor would not publicly record until a few years later. Many (middle class) African-Americans at the time saw this kind of humor as an embarrassing throwback that would hurt their chances of integrating into mainstream America, thus it was heavily criticized at the time.
But taken as it is, the sometimes bawdy tales like "Shine and the Titanic," "The Signifying Monkey" (the title of the book is the opening stanza from this), "Stagolee", "The Preacher and the Bull," etc. were street folk tales that were told for years in Black communities. Previous folklorists such as Langston Hughes tended to clean them up for public consumption. But the fact that these tales were told in the streets for so many years is proof that for better or worse, what we now know as "Gangsta Rap" is nothing new.
Incidentally, the story of Roger Abrahms's experiences getting these tales in the Philadelphia ghetto and the initial controversy behind this book would make an interesting movie.