The typical sci fi book should have enough science in it to tell the story, and nothing more.
Conflict, and how the protagonist deals with that conflict, drives most good stories. Science interprets the reality of the world around us. By itself, science has no conflict.
Science is a secondary character in most novels. Devoting pages at a time to a secondary character is usually a mistake. I learned this from experience. When I first submitted Truth-Teller Rebellion to Champagne Press, it came back with a rejection, but with the comment that if, among other things, I wanted to eliminate the excess description (science in most cases) I could resubmit it. Thank you Champagne Press for that second chance. An example given was the two pages I had devoted to a detailed explanation of the construction and operation of a solplane. The editor was right. My two pages on solplanes just slowed down a story that already was a little too slow.
Often, a scientific idea is the spark behind a novel. For example, what if artificial intelligences no longer need mankind? That is the basis of The Fall of Hyperion and 2001: A Space Odyssey. However, what keeps the reader turning the pages in these classics is how the protagonist deals with this obstacle, not the science of artificial intelligences.
I recently read Anathem by Neal Stephenson. I admire this book for its originality, but the science of this book slowed it down. Anathem’s thesis centers on the many-worlds interpretation of quantum mechanics, MWIQM, which is roughly akin to the parallel worlds that inhabit many sci fi novels. I read the first discussions of MWIQM with care. However, there were more talking head discussions about MWIQM for pages at a time. I skipped over them all. Some quantum mechanics geeks might like these interruptions to the story, but they are a fine slice of the reading public. I suspect most readers will react as I did.
Putting science in a novel in most cases means more description. I like to get poetic with my descriptions. It pleased me that longandshortreview.com said in its review of Truth-Teller Rebellion that “Mr. Schultz’s scenery descriptions are not to be missed.” I was flattered, but that doesn’t mean I should write more and longer descriptions. When I’m writing my best, my descriptions mesh seamlessly with the dialogue and action.
Science is important to science fiction, but unless you want only hardcore science geeks for readers, keep the science short and sweet.