jhānas, Zen, and how to practice concentration meditation I've read about the jhānas which one can experience from concentration (samatha) meditation. I have been practicing some form of mindfulness, breathing meditation, but have not experienced a state of absorption that is characteristic of the jhānas. I know that the jhānas cannot be experienced only by reading about them, however, the insight from my meditation practice alone has not brought me to them.

From my perspective as a novice practitioner, it makes sense to look to the Zen (derived from the word dhyāna) branch of Buddhism for guidance on the subject of meditation:


  In the process of deepening meditation, one can roughly identify three
  distinct stages: the stage of concentration, the stage of meditation,
  and the stage of absorption. 
  
  This dualistic relationship is broken gradually as the practitioner
  moves into the stage of meditation. The ego-conscious activity is
  gradually lessened, and the barriers it set up for itself will
  gradually be removed. When the practitioner enters the stage of
  absorption, the dualistic framing of the mind will be removed such
  that the mind starts structuring itself non-dualistically. There will
  be no separation or distancing between an object of the mind and the
  activity of the mind itself.


I don't have the budget for every book on Zen Buddhism, but I have read all the Zen books on Kindle Unlimited (the content is mostly history, terminology, and sitting accessories). What books are there that go into depth on Zen/samatha meditation practice?
A true Jhana master, Venerable Pa Auk Sayadaw:


Breakthrough in
SAMATHA MEDITATION
Knowing and Seeing (4th revised edition)


And if you can purchase this book, I highly recommend it:


Practicing the Jhanas: Traditional Concentration Meditation as Presented by the Venerable Pa Auk Sayadaw


It's written by actual students of the Venerable Pa Auk, who actually succeeded in developing the Jhanas: very clear and concise, with practical advice.