As a matter of fact you can get at least five of Earl Der Biggers' novels (plus a non-Chan extra) at http://gutenberg.net.au/crime-mystery.html:
The House Without a Key (1925)--Text--ZIP
The Chinese Parrot (1926)--Text--ZIP
Behind that Curtain (1928)--Text--ZIP
The Black Camel (1929)--Text--ZIP
Charlie Chan Carries On (1930)--Text--ZIP--HTML
Keeper of the Keys (1932)--Text--ZIP
