Bernard McGinn's The Presence of God: A History of Western Christian Mysticism
The Foundations of Mysticism: Origins to the Fifth Century (The Presence of God: A History of Western Christian Mysticism Vol. 1 http://smile.amazon.com/Foundations-Mysticism-Origins-Presence-Christian/dp/0824514041/ref=la_B001IXMTXE_1_3?s=books&ie=UTF8&qid=1449798210&sr=1-3
The Growth of Mysticism: Gregory the Great Through the 12 Century (The Presence of God) (v. 2) http://smile.amazon.com/Growth-Mysticism-Gregory-Through-Presence/dp/0824516281/ref=la_B001IXMTXE_1_5?s=books&ie=UTF8&qid=1449798210&sr=1-5
The Flowering of Mysticism: Men and Women in the New Mysticism: 1200-1350 (The Presence of God) http://smile.amazon.com/Flowering-Mysticism-Women-1200-1350-Presence/dp/0824517431/ref=la_B001IXMTXE_1_8?s=books&ie=UTF8&qid=1449798210&sr=1-8
The Varieties of Vernacular Mysticism: 1350–1550 (The Presence of God) http://smile.amazon.com/Varieties-Vernacular-Mysticism-1350%C2%961550-Presence/dp/0824599012/ref=la_B001IXMTXE_1_2?s=books&ie=UTF8&qid=1449798210&sr=1-2
Other books by McGinn are also very appropriate for inclusion.