This low price Classic has perhaps been mentioned in past years, but I don't see it in this thread.
Mark Twain's
Life on the Mississippi is a free kindle book today.
https://www.amazon.com/Life-Mississi...ital-text_f_77
This opens up two of the Audible versions as low price whispersync deals, one 49 cents and one 99 cents.
http://www.audible.com/pd/Classics/L...8179917&sr=1-1
http://www.audible.com/pd/Bios-Memoi...8179917&sr=1-4