It's only fair that I give you my thoughts -- in a harmless, spoiler-free way.
I read book one. I read it quite a long time after it came out, because assorted people were talking about it, and I thought it was the sort of thing I ought to have read. I ended up half-enjoying it.
I read book two. I read it because I'd sort-of enjoyed book one, and for complicated reasons we had three copies of it in the house and I was going somewhere where I didn't want to take a book that had to be kept in good condition. I think it was a boating holiday or something -- and I wanted a book I could cheerfully write off if I dropped it into the river. It was sort of okay.
I read book three. This was because some clown online was going on and on about slashing some of the teachers, and I wanted to see what all the fuss was about. I never really got Sirius/Remus from having read the book -- it was only having seen the movie, years later, that I finally worked out that the pairing was going to work. This was probably more to do with the actor playing Remus than any of the actual writing.
I started book four. It was a bit of a shock when I first picked the book up, because it weighed approximately the same as the first three put together. It was very hard going, very slow. I theorised that the publishers had decided that the book would still sell even if they didn't bother employing an editor, and I believe the book suffered for it. It was dire. I finally gave up a little less than half-way in.
I didn't read book five. I thought that if she couldn't sustain my interest through a staged battle between her main protagonist and a big scary dragon in the previous book, then she didn't stand much chance of sustaining my interest through another book that generated a gravitational field of similar strength. I had better things to do.
Much the same reasoning is keeping me from starting out on book six.
(Spoiler-free, in this context, means free of spoilers for book six. There are spoilers above for books three and four)