It's tough to reveal some of it since it's a spoiler either for the novel or the other adaptations. I'll try to be vague. If I recall correctly, you can get the gist by reading the first chapter or two of the book.

The Spacing Guild is a much more important aspect of the story than what the new adaptation made of them. In fact, they are a prime mover of certain character motivations. In the Dune universe there are two schools of thought, the Bene Gesserits and the Spacing Guild. I don't think viewers of the new adaptation could even say what the Spacing Guild does even though I think they are way more interesting than the Bene Gesserit.

There was also an interesting fighting technique the Bene Gesserit practiced called the weirding way. The new films seemed to have none of that, either.