I have read these many, many times (though, it has been several years). I love reliving the characters and the scenes each time. I loved this just as much as I first read it when I was a kid. I'm re-reading these in time for Cursed Child and can't help but feel like I'm going to be a tad bit disappointing in the new one -- I hope not though!
Its year three at Hogwarts for Harry and his friends. But things aren't going exactly as planned. Harry is being watched closely by Dumbledore, the professor's and even the minister of magic. Sirius Black is on the loose, escaped from Azkaban and after Harry of course!
I love book three because of the introduction to the Marauders. I think they're my favorite characters in the entire series.