I've been thinking about whether an author's intentions when writing a book contribute to my actual perception of the quality of the book. And I think they do.
Not in any deep way, but if I feel like an author's writing with the creation of commercial goods in mind, their book had better be pretty damn good if I'm going to feel like it was worth reading. It should be either really fun to read, or really well written, or both, but if it's mediocre it's just like any other piece of merchandise - if the paint is bad quality and pieces look like they're going to fall off, what's the point?
On the other hand, if I feel like the writer is writing primarily for personal satisfaction--they enjoy it, or they want to explore some ideas, or they want to see if they can do it--I can be a lot more lenient. They're not trying to foist anything on me, they're just offering their handiwork for sale. So if it's fantastic, it makes it all the more special, but if it has some rough edges that just adds to the charm.