If you are interested in Ignatian spirituality there are a lot of resources. Start by reading Ignatius’ biography, which is really wonderful and quite winsome at the same time.
I think the best way to understand mysticism is to start by reading the mystics themselves, the easy ones that is. Then pick up a few books of commentary on the text. I have found the following very fruitful: Catherine of Siena’s Dialogue; Teresa of Avila’s Interior Castle; Julian of Norwich’s Revelations; John of the Cross’ Dark Night of the Soul. Hildegard of Bingen is off-the-wall interesting and she even illustrated it with her apocalyptic visions (just avoid the Matthew Fox version). Bridget of Sweden’s work is less accessible, I think, but still powerful in small doses. I still don’t know what to think of Catherine Emmerich and only skimmed through parts.