Reddit reviews The Science of Dune: An Unauthorized Exploration into the Real Science Behind Frank Herbert's Fictional Universe (Psychology of Popular Culture)

Cool find!
If you're into the Science of Dune, you owe yourself a read of - literally - The Science of Dune, a compilation of essays by notable, credentialed authors on various aspects of Dune's biology, ecology, technology, culture, astronomy and more. Genetic memory, stillsuits, the physical location of Dune (which is a real planet!), anti-gravity... It's a great read.

I know it is unpopular around here, but I would recommend reading the Brian Herbert/Kevin Anderson books a read. Borrow em from your library if you are nervous.

Nothing as cerebral as Dune but I am a big fan of John Ringo's stuff. He had a collaboration with David Weber that was good "The Empire of Man" which begins with "March Upcountry".

I also started The Horus Heresy series and am on book 9 and cannot get enough.

There is The Road to Dune which sheds some more light on Frank and the development of the original novel.

There is Dreamer of Dune which is a biography of Frank.

Last but not least, this book is kind of cool: The Science of Dune. It is a collection of essays by scientists and philosophers about different aspects of Dune and their scientific foundation (i.e. could Arrakis exist). Disclosure, the links I provide might be an affiliate link.