keyword: Chaucer, Geoffrey, -1400 – 5 free books.
These books are included in Project Gutenberg. They are archived and can be improved at GITenberg.
The Canterbury tales
Chaucer's Official Life
James R. (James Root) Hulbert
Chaucer and His Times
Grace E. (Grace Eleanor) Hadow
Chaucerian and Other Pieces
Being a Supplement to the Complete Works of Geoffrey Chaucer
Walter W. (Walter William) Skeat (editor)
Adolphus William Ward, Sir