Never dreaded any chapter, and that's pretty rare for me. I mostly just browse through a chapter of a book because it becomes boring or seem useless to me. Sphere on the other hand was very consistent, consistent with suspense. You never know what could happen next and there were a lot of twists in the story.
my favorite character from the book would have to be Ted, and up to now it still annoys me that he had to die. No problem with Harry and Beth though. Right from the start I knew Harry would make it till the end, but I expected Ted to make it and not Beth. It could be a manifestation of Crichton not being sexist, and giving importance to females. That's just my opinion though.
An easy recommendation for Sci-Fi fans, or even a normal reader who seeks suspense and thrill plus a very good plot that has been written very well. Crichton never fails to amaze me.