Benedicta Ward (translator) The Sayings of the Desert Fathers  Cistercian Publications 1975

Carmen Acevedo Butcher (translator) The Cloud of Unknowing Shambhala  2009 (There are various translations available but I recommend this one)

Guigo II  Ladder of Monks and Twelve Meditations  tanslated by Edmund Colledge and James Walsh, Cistercian Publications. 1979

Olivier Clément The Roots of Christian Mysticism New City 1998 (Get the 2nd edition if you can, it has an index, which is invaluable!) I can't commend this book highly enough!

Benignus O’Rourke Finding Your Hidden Treasure DLT 2010

Cynthia Bourgeault The Heart of Centering Prayer: Nondual Christianity in Theory and Practice Shambhala 2016

Enzio Bianchi Lectio Divina SPCK 2008

Wyn Beynon For This I Came Canterbury Press 2023 ( I can't commend this book highly enough, either... but then, I wrote it!)

You can pick up second hand on t’internet…

Robert Llewelyn (editor) The Joy of the Saints: Spiritual Readings throughout the Year DLT 1988 and offprints of this in little books in the  Enfolded in Love series

Anything by Fr Thomas Keating or Richard Rohr or Cynthia Bourgeault.