St. theophan the recluse, st. john of the cross, have all been mentioned, so I’ll other than them go with someone else
st. faustina, for showing us the mercy of God and defining it through her works and life and prayers
st. gemma galgani, for showing us most clearly (at least to me, I havent read about many others) what being a victim and lover of Christ is like
st. Anne Catherine for her records of the life of the Lord and His mother, St. mary of Agreda and Ms. Maria Valtorta all also contributed to this, I love their works so much and they will personally guide you to the Cross, where you will win salvation for yourself and others, by more fully illuminating the Gospel lives of Our Lady and Lord
Jacob Boehme for writing about the highest mysteries of God, yes he did make errors but that is not to detract from his glory, as he is one of the few mystics who illuminates what WISDOM is and where the origins of the world are. if you read him closely, shifting out any error, and experience his writing in your own mind and soul, you will come to a great peace and knowledge that God is Lord, the world is beautiful, and heaven is at hand. he is a unique mystic in that he doesnt write or flesh out the gospel, isnt about how the love of God was experienced in himself, but is primarily writing about who God is and what God is and how God is
norman grubb, another protestant and interpreter of Boehme, he talks about Christ in us, and this changes ones perspective on all things.
Angelus Silesius, specifically for his work Cherubnic Wanderer, he is a Catholic priest and interpreter of Boehme. his two-line poems reduce all of Christianity to its simplicity, the paradoxes he draws out are beautiful, and meditating on them to come to God is a fruitful endeavor. they contain all you need to know, love, and serve God, every single thing. He begins with who you must become
I dont know anyone else for now, but these, other than who has been mentioned, are my favorites