Here’s a ticklish one! Just which is most important to the average reader: the content of the story or the quality of the writing? I know that I read certain works despite the fact that they are, in fact, not particularly well written, because I admire the breadth of imagination that has gone into them. So, in those cases, it’s definitely substance over style. Oddly, however, I still get immensely annoyed at printing errors! Typographical errors are all too common, and then you get the split text, which is awful. By split text, I mean where, say, a paragraph is suddenly, rudely interrupted by a later passage, only to be taken up again a while later. I assume such things happen when something new is added but entirely the wrong location!
But to get back to the root question. I can forgive a lot, if a story demonstrates an excellent vision. The problem for me lies in discovering the good story before the poor quality of writing overwhelms me. Most of the books that I re-read and suffer from poor writing, I originally read in my childhood or youth. Obviously, my standards were lower then, with less knowledge of good style. It irks me somewhat that I may be missing out on superb displays of imagination because I have now grown up and expect better writing. Only if the story races along does it have a chance of getting beyond a few pages of reading, now.
I’d be very interested to hear from others what their views are.