Besant, Walter. All Sorts and Conditions of Men. Oxford University Press, 1997.
Booth, Charles. Life and Labour of the People in London. 17 vols. London, 1902.
. Charles Booth's London: A Portrait of the Poor at the Turn of the Century, Drawn from His Life and Labour of the People in London. Selected and edited by Albert Fried and Richard M. Elman. New York: Pantheon Books, 1967.
. See the LSE website at http://booth.lse.ac.uk/.
Includes a great deal more than everything you could possibly want to know about conditions for the poor in this time period. Booth also put together a color-coded map of wealth and poverty in London, which is available at the website above, browsable. The LSE website also has Booths notebooks, which are fascinating by themselves, if a little tricky to read. The selected hot-bits version by Fried and Elman is excellent.
Greenwood, James. A Night in a Workhouse. Pall Mall Gazette, 1866.
Greenwood, James. The Seven Curses of London. Stanley Rivers, 1869.