It was okay.
It was not terrible, but it certainly was not great. The miniseries was probably better.
Some of the casting was poor, but Isaac and Ferguson did well. It's usually a shame for a movie maker to exchange an author's vision for his neighbor's expectations & sensibilities This keeps happening.
It doesn't help to tell the audience how to interpret a story's ending just after the opening credits. A well-told story leaves the viewer the pleasure of figuring that out for himself.
Having read the book tends to ruin a mediocre movie, even if it was only the first volume and a long time ago.
This is the second reboot of Frank Herbert's novel. Maybe it would be better to stick to rebooting botched things, things you're sure you can improve on.