These books are a little obnoxious in the sense that their author's started goal was to write a shorter, less complex novel, but instead wrote four (maybe more?) shorter novels in serial fashion. As best I can tell, this is really a 1,000 page novel in disguise.
To call them hard sci-fi is a stretch. "Space opera" is more appropriate. They read more like a Star Wars novelization than, say, an Arthur C. Clarke novel, and for all of their exploration of alien worlds, they're not dissimilar from fantasy novels. They lack the technical description and sense of realism that I expect from "hard" sci-fi, but Wikipedia tells me that's a term with a broader meaning than what I assign it myself.
They are fast, engaging novels, though. The concepts are often difficult to envision, or at least too abstract. I'm still not sure how to imagine a "magellan-fish," for example.