Self-publishing is the way to go. I built my own platform to sell my book Mastering Modern Payments[1] but if I were starting from scratch I would strongly consider something like Softcover.
Since launch it's made approximately $35k. Not quite the solid success that the OP talks about, but then again I invested far less time than the OP suggests.
Since launch it's made approximately $35k. Not quite the solid success that the OP talks about, but then again I invested far less time than the OP suggests.
[1]: https://www.petekeen.net/mastering-modern-payments