Yep! Do that all the time with online stories. Bad writing, no discernable plot or the plot just falls apart, an inordinate amount of time between chapters, etc.
Dead tree books? I have my favorite authors (Raymond E. Feist, Janny Wurts, Joan D. Vinge, Jerry Pournelle, Larry Niven and a few others) and I usually don't bail on one of their books, but it has been known to happen.
Back when I first discovered LOTR, I bought all three books. Started Fellowship of the Rings and didn't get past the first chapter, put them on the bookshelf and forgot about them. Then sometime later, I read an article about how they were all the rage on college campuses. I remembered that I had the books and wondered what was so great about them and started to read them again. This time I went through all 3 books one right after the other. Then went back and got the Hobbit and read it.
Because of the time lag between chapters of online stories, if I'm really enjoying the story, I'll likely re-read, at least parts of it, while waiting for a new chapter. Usually, when I do that, I discover little things that I've missed the first time around. Jamie's The Scrolls of Icaria is one such story. There are many little gems that I've discovered in re-reading all or parts of the story. But, there again, a story has to be well written with all of the elements that hold my interest.
By the same token, I frequently re-read dead tree books. With books in a series I'll start with the first book and continue through all of them.