Eikon Basilike was a book of the prayers and meditations of King Charles I during his last months. It was said to have been compiled by the King himself, though it was probably written by Doctor John Gauden based upon the King's papers.
First published in February 1649, Eikon Basilike proved extremely popular and ran to 36 editions. It presented the dead King as a victim of tyranny and a Christian martyr. Other tributes soon followed, in which explicit parallels with the sufferings of Christ were drawn, leading to a Royalist cult of Charles the Martyr. John Milton wrote Eikonoklastes ("the image breaker") as a counterblast.
Several churches were dedicated to Charles after the Restoration, and the feast day of Charles King and Martyr is still celebrated in High Anglican churches on 30 January, the anniversary of his execution.
Eikon Basilike, edited by Edward Almack [offsite]
Society of King Charles the Martyr [offsite]