Harry Potter

After avoiding it until it was over, I read through the entire Harry Potter series this summer, beginning with The Philosopher's Stone in August and wrapping up with The Deathly Hallows sometime in November. (They're pretty quick reads, even the longer books in the series). I did see the first three movies when they came out in theatres, and of course it was nearly impossible to come to the series at this late date without some idea of what the books entailed.
With an initial read through the books, it's easy to understand why they are so popular. The story, which of course centres around Harry and his encounters with Lord Voldemort, is interesting and kept me reading until the end of the series, because I wanted to know how it turned out. On that basic level, J.K. Rowling succeeded admirably.
That success, I believe, stems not from an original, carefully crafted story, but rather from the characters she created back at the beginning of the series. Indeed, the story itself is fairly boilerplate stuff; pick up any other fantasy epic aimed at young readers, and it will probably feel very similar. The plots are serviceable, but don't support too much thinking - witness the huge plot hole that encompasses most of book four. What made the Potter series interesting was the characters; I kept reading because I wanted to see how Harry, Ron and Hermione would deal with the situations they faced, and how the situations affected them.
It's a testament to Rowling's imagination that she was able to create such vivid characters. It's not just true of the main characters, either; even the secondary characters, usually, have quite a bit to them and evoke the empathy of the reader.
The one drawback to the characters is that they don't develop much over the course of the series - especially considering the main characters age from 11 to 18 during the seven books. While for most people these years constitute a lot of growing up, for the main trio very little is different. Harry and Ron are each introduced as fun-loving, a little bit afraid of attracting attention and with almost no interest in homework. This never changes, even when they decide they want to become aurors. (Likewise, it seems every book features Hermione finally overcoming her goody-two-shoes nature, only to be right back at it in the next one). Harry basically never overcomes his largely irrational hatred of Snape, even though he is proved wrong many, many times over the course of the series (although it may be worse that Snape and Sirius Black, grown men and presumably mature characters, are also unable to do this). Secondary characters, like Neville and Ginny, do change and mature, but they do it off-page; all of sudden, they've become different people. It was for this reason I was a little disappointed in the ending; as I was more interested in the characters than the plot, I would have liked more reaction than a simple climax. How did the final events affect the main characters, and how would their lives change? The ending, even the epilogue, don't give much of an answer, in my opinion.
Rowling is not a great writer, in the sense that if people admire these books in 100 years it will be for the characters and the story, not her language. To her credit, though, her writing did seem to get better over the course of the series. The first three or so books were full of cliches; at one point, I think at the beginning of Goblet of Fire, I told Chelsey that if Harry, Ron and Hermione went to the candy store and came back "with their money bags considerably lighter" one more time, I was going to throw the book across the room. I didn't throw any books, and while perhaps that was because the main trio didn't go to the candy store in the final books, I think it was because Rowling's writing was more careful.
Despite that, I think the best book of the series remains the first one. It was here that Rowling was able to show off her greatest strength, her powers of invention. She created her own world, but it wasn't a completely separate world like Middle Earth, it was a world within our own. Because of that, many of the things Rowling includes are at once familiar and yet delightfully new. Her imagination for the details that would make up a magic world embedded in our own is amazing, and usually spot-on. These details are sometimes satiric (the Ministry for Magic) and usually humourous. In the first book we get to discover this world along with Harry. Indeed, Philosopher's Stone reads less like an epic and more like a series of adventures only semi-related to each other. (For this reason, I think Potter would have made a better TV series than a movie franchise, but I guess there's more money to be made in movies). Even by the end of the first book, however, some of the inventions hit their limitations; Harry, Ron and Hermione are put in a tough spot by the slow nature of owl post, when any muggle teenager would be able to IM or use their cell phone in a flash. And as the series goes on, there is less to discover, and that's a shame.
Still, as I said, those characters that Rowling introduced in the first book were good enough to keep me reading and engaged through the seventh book. It's not perfect, but it's good enough.