The best single source for information about Machaut, his manuscripts, and his works remains Lawrence Earp, Guillaume de Machaut: A Guide to Research, Garland Composer Resource Manuals 36 (New York and London: Garland Publishing, Inc., 1995).
A new edition of all of Machaut's literary and musical works is underway as part of a collaborative project led by Yolanda Plumley and R. Barton Palmer. Details about progress and publication can be found at their website The Works of Guillaume de Machaut: Music, Image, Text in the Middle Ages.