**The Cambridge Companion to Medieval English Theatre ed. Richard Beadle, Cambridge 1994.
R.W. Southern: Medieval Theatre in the Round
R. Weimann: Shakespeare and the Popular Tradition in the Theatre.
S. J. Kahrl: Traditions of Medieval Drama
C. Richardson and J. Johnston, Medieval Drama, Macmillan 1991
N. Denny (ed.) Medieval Drama (Stratford on Avon Studies 16)
link to: medieval
Middle English plays
a) Mystery Plays
You should read the plays of the Wakefield Master, one of the Abraham and Isaac plays, and the York Harrowing of Hell (in Fourteenth Century Verse and Prose): also the work of the 'York Realist': York 26, 28-33, 36. ?
most available in Mystery Plays, Penguin, ed. P. Huppé
R. Woolf: The English Mystery
V.A. Kolve: The Play called Corpus Christi
J. Taylor and A. Nelson: Medieval English Drama: Essays Critical and Contextual (1972)
look at H-J. Diller: 'The Craftsmanship of the Wakefield Master', J.W. Robinson: 'The Art of the York Realist' and L.Ross. "Symbol and Structure in the Secunda Pastorum".
link to: York Doomsday project
b) Morality Plays
You should read Everyman, Mankind, The Castle of Perseverance and Wisdom.
See especially P. Neuss' article on Mankind in Stratford on Avon Studies 16, as above
R. Proudfoot, "The Virtue of Perseveraunce", in Aspects of Early English Drama. ed. P. Neuss (1983)
Essay on Mankind, subversion and carnival in D. Aers'(ed.) Medieval Ideology, Criticism, History. (1986)
Gail McMurray Gibson, The Theater of Devoiton: East Anglian Drama and Society in the Late Middle Ages Chicago, 1989
Baragona's medieval drama page
Hanly's medieval drama page