As far as I know sufi path is based on spirituality (batin) which has the sources from Ahlulbayt.. But, in the end they attain the spirituality through the visuals (zahir).. and in the visuals and practices they either follow sunni or shia madhabs.. the shia Jaffari ones stressing more on spirituality are called; arifaan; (the ones practising irfaan or Marifa as brother yusz mentioned being the last stage.. which is a branch of shia islam).. about the sunni ones (Tasawwuf), they also believe in 12 imams as described by shia islam.. so, in the end, they are shia arifaan in belief but regarding madhabs tasawwuf follow sunni interpretations..
and you can study Irfaan, the fourh stage of sufi faith as brother yusz mentioned with the books like:
"Light Within Me" by Ayatullah Mutahhari, Allamah Tabataba'i, Imam Khomeini
"Spiritual Discourses" by Ayatullah Murtaza Mutahhari
"Elixir of Love" by Muhammad Rayshahri
Lubb al-Lubab (The Kernels of Kernels) - Short Treatise on Wayfaring by S. M. Husayn Husayni Tehrani (qs)
Forty Hadith: An Exposition by Imam Khomeini
The Greater Jihad by Imam Khomeini,
"Lantern of the Path" by Imam Ja'far al-Sadiq (a),
Spiritual Journey of the Mystics (Suluk al-Arifan) by Haj Javad Maliki Tabrizi
The Wine of Love : Mystical Poetry of Imam Khomeini (if you read this, please don't take the terms in his poetry as zahir/literally..)
Perfect Man by Ayatullah Murtada Mutahhari
Inner Secrets Of The Path by Sayyid Haydar Amuli
An Introduction to 'Irfan by Martyr Murtada Mutahhari
Risaleh ye Sayr wa Suluk: A Treatise on Wayfaring by Bahr al Ulum (qs)
Adab al-Suluk: A Treatise on Spiritual Wayfaring by Shaykh Najm al-Din Kubra
Islamic Gnosis ('Irfan) and Wisdom (Hikmat) by Muhammad Taqi Misbah Yazdi
Self Building An Islamic guide for Spiritual Migration towards God by Ayatullah Ibrahim Amini
Sahife Sajjadiya by Imam Sajjad
Soaring to the Only Beloved by abu Muhammad Zaynul 'Abidin
I read some of them.. especially the ones by Imam Sajjad, Imam Khomeini, Murtaza Mutahhari and Tabatabai (Tehrani).. They really are amazing..
Thanks.. and thanks for the videos, yusz.. Ma salam