The Prince and the Pauper

This is one of Twain's "softer" books - although there is some social criticism and a few sad episodes, by and large this is a delightful story with many humorous incidents.  And the overall theme of the book is a paean to mercy - sympathy for one's fellow man and a willingness to help.  The device of virtual twins, one from the highest and one from the lowest station of life underscores that, as the Phil Ochs folksong says, "there but for fortune go you or I".  And Twain is a masterful storyteller with a powerful ability to build a mood and then demolish it suddenly with a piercing incident (no spoiler quote to follow!)  Very highly recommended.