First off, I know what you're thinking. "Dude, Harry Potter ended ages ago, get over it, you're kind of late for this". I know that but I've just finished reading Abhorsen, the fantastic third book in the Old Kingdom series (for more on that read my post Nothing Like A Good Book where I talk in part about this series, but mainly the first book).
While I was reading this series, I thought I might as well reread Harry Potter when I was done with it, I had been meaning to reread them, and reading one book about magic and what not makes you want another. So I have a choice now between Harry Potter and the "sequel" to Abhorsen. It's called Across The Wall, and it's a series of short stories based after the last book. I tried to read it before, but I just couldn't get through it. I think it was because it had less of a feel of adventure than the other ones. I'll probably give it another go though, and if I fail to read that, or after I do read it, I'll probably start work on Harry Potter, which brings me to the subject of Harry Potter. Damn I'm good.
I'm only going to talk exclusively about the books if I can help it. I've watched the first four movies, and that was way too much for me. The fifth book, Order Of The Phoenix was my absolute favourite book of the series and I didn't want to see what they were going to do with it after what they did to the first three, and I've heard reports that make me mourn the series, especially about the sixth movie. They cut out something near the end that I felt really needed to be a part of it, but I hate spoilers. I've also seen people get confused by things that happened because stuff was cut out in the movie process. Dear JK, how much did they give you for your integrity? Was it worth it? Still, I love Ed Byrnes joke that he hasn't read any of them, but he's seen them all with subtitles, so he has technically read them all.
The books are really good, there's more to them than the movies, and things just feel a lot better. Plus you don't have to deal with how creepy it is that a girl we were introduced to aged 11 has now become a sex symbol. Way to go. Still, the same thing happened to the Olsen Twins and pretty much every female child actor. So that's nothing new really.
I watched the movies before I read the books, I actually watched the second movie before the first. I forget how I came to watch the second movie, but I got the first for Christmas, because I liked the second. I ended up reading the books, I think to find out what happened next. Which is also how I came to read a lot of manga, but, as usual, another story. I found myself surprised by what was left out, for example in the first book Harry and Malfoy actually attempt to have a magical duel (something that was later done awesome in one of the movies, yes I'll admit some of it was cool). I will admit, like I just did, that things like the magic, and Quidditch made for good stuff in the movies, it's easier to watch action than read it, but, eh.
Although I did earlier claim that the fifth book was my favourite, the third would have to be just behind, if not joint. I loved Sirius Black, he was a wonderful character, and my favourite. The Harry Potter world does have some really good things in it, and the books have a lot more, so if you've watched the movies, but not read the books, I say read them if you liked the movie, you might even like the book more.