The Pilgrim's Progress
The book uses the dream story of a journey through the English county of Bedfordshire, to London. Bunyan uses this to tell the idea of Christianity from a Protestant point of view. Although the journey is imaginary, the places are based upon real places in 17th century Bedfordshire. The difficulties faced by Christian, the main character, is meant to be an allegory of the difficulties faced by a true Christian in keeping to the 'straight and narrow path'.  The author was jailed for preaching his opinions, yet after the book was published, it was translated into over 200 languages.