For an easy to read edition of the Eikon Basilike, check out these free digital copies available online:
Project Canterbury offers an HTML version of the text with images.
Project Gutenberg offers an HTML version and various electronic formats for download, including a mobile version and a Kindle edition.
Google Books offers both an HTML version and downloadable versions.
Below are secondary sources about the Eikon Basilike within Special Collections.
To find more secondary sources about the Eikon Basilike within Special Collections advance search the catalog for "Eikon Basilike" in all Marylandia and Rare Books collections.
A Vindication of King Charles the Martyr: Proving That his Majesty was the Author of Eikon Basilike by 
"Who wrote Eikon basilike?" considered and answered, in two letters, addressed to His Grace the Archbishop of Canterbury by 