Bonnie Greenwell, Ph. D. not only had her own Kundalini activation but also works as a Consultant in that field since many years. She also wrote very helpful books:
Adyashanti does not make a fuss about his person nor the process. It was him who showed me the most helpful approach in just telling it over and over again: It actually is just a shift in consciousness, in how you perceive reality. Even the so called "Enlightenment" is not going to Lala-Land and being happy ever after... it is a long and sometimes rough journey to and with yourself.
Mary E. (Betsy) Rabyor has a good webpage with a lot of first hand accounts of her own experiences in the process.
Jiddu Krishnamurtis teachings are of immense value. And from an untameable spirit, renouncing fame and fortune for the freedom of breaking the build up of new doctrines.