Ken Wheeler has some interesting insights into it, and there is a lot of reading material also linked in the description of his videos.
The other option would be to go to the sources of much of the research, usual suspects like Tesla. But it is a lot to dig into if you don't have an overview or understand a lot of the terminology, which is where I was about 6 months ago with all of this. The books about it are quite technical, especially when comparing the atomistic approach - The Lightness of Being by Frank Wilczek is a good book which talks about unifying the forces, which is impossible if one ignores the aether.