Jack London 
People of the Abyss 

"The People of the Abyss" (1903) is a book by Jack London about life in the East End of London in 1902. He wrote this first-hand account after living in the East End for several weeks, sometimes staying in workhouses or sleeping on the streets. In his attempt to understand the working-class of this deprived area of London the author stayed as a lodger with a poor family. The conditions he experienced and wrote about were the same as those endured by an estimated 500, 000 of the contemporary London poor. London also used the expression "the people of the abyss" in his later dystopian novel "The Iron Heel". (Wikipedia)