I know I'm chiming in late, but who cares:
I think Harry Potter is great. I got into it a little after the 4th one was released. It's a great easy read... and it usually goes pretty quickly too. It's good for reading while gearing up for your next intellectual read.
I enjoyed all the books. Number 5 was my least favorite, though. It was borderline boring and very exhausting to read, but it did have some necessary information in it, so it couldn't be done without. It was kind of like reading 3d posts. Not exactly desireable, but necessary to understand all the jokes.
I think the movies brought a lot of attention to the series, but also may have ruined the experience ( and yes, it is an experience) for people who would have otherwise enjoyed the series. Had I seen the first movie before reading any of the books I never would have been a fan.
I assume by the 4th you meen the 4th grade .