This book is a great starting point, Atwater began the project that later became Project Stargate. It is very mundane in tone, focused on the development of military procedures. Joseph McMoneagle is probably the star of that project and also worth a looksee.
For general consciousness discussion I would highly recommend Russell Targ Limitless Mind. Even the stuff Joe Dispenza puts out is similar and related.
I would say these sources are all great to dip your toes in without diving into the deep end. It's my personal pet project if you ever want to have a chat about it I would love to connect, I promise to take it easy at first, baby steps!
https://www.goodreads.com/book/show/865520.Captain_of_My_Ship_Master_of_My_Soul