The first several books are, generally speaking, Who-done-its with supernatural aspects. Some are murder mysteries, except the murderer is a werewolf and you have to figure out what kind of werewolf it is before even taking steps to discover the killer. Who knows? Maybe finding the killer will just make you end up dead because if a four hundred pound murder monster is caught he's not going to sit down quietly while you handcuff him and put him in the car.
So, Jim Butcher throws us into this universe and does a great job explaining real world anomalies with supernatural causes. Since this is an urban fantasy, this series is essentially the real world, and the reason that people don't know that faeries exist is complicated, yet logical. Long story short, the public doesn't know about the supernatural world because we don't want it to exist so we refuse to acknowledge its presence. Which, in my opinion, is a valid explanation. I have no problem suspending disbelief on that because I feel as though all of that stuff did exist and we didn't know about it, that would be why.
Another fantastic thing. Stories told in first person can be forced to be good as long as the main character is interesting enough to keep you invested. Harry Dresden is an extremely powerful wizard that could probably take a side job as a comedian if he had the time. I'll include a quote of dialogue example, and let me just say it was hard to pick just one out of a pile of gold.
"If I need you, I'll give a signal."
"I'll imitate the sound of a terrified little girl."
But by far, the best thing about this series, is the most defining feature of Dresden Files. Harry Dresden has an impeccable knack for making his situation impossibly and horrendously worse for himself. I won't provide examples for obvious reasons, but its amazing because, somehow, Butcher writes these scenes in such a way that I personally don't ever get frustrated. When Harry makes the baddie that much more scary, I'm amused rather than frustrated. Sure, Dresden can be pretty dumb, but he still does a good job (eventually) solving problems and beating the monster.
Another thing is that, unlike most books I read, I actually like almost every character. Obviously I like everybody for different reasons, but I'm always happy to see whats happening with other characters. In fact, I can only think of two different parties off the top of my head that I'm uninterested in. Everybody else is pretty much awesome int heir own right.
The only substantial criticism I have for this series, is that the first two book are legitimately bad. These were the first two novels that Jim Butcher ever published, mind you, and it shows. Most things are painfully obvious when they shouldn't be, and the only times that consistently throw you off guard are the things you simply cannot predict, because you're not familiar with the supernatural yet. In the second book, Fool Moon, there are about four (or more) different types of werewolf, and even though this is a short book, Butcher sees fit to squeeze every single type into its pages. Its overwhelming, but it gets better, I promise.
Grave Peril, the third book, is when it actually starts to get good. It introduces a few of my favorite characters in the entire series. Death Masks, the fifth book, introduces my favorite antagonizing force, and Dead Beat, the seventh book, is just incredibly epic for so many reasons its not even funny.
So, if you read Harry Potter as a kid and want something in that genre for your age, this series is a must read. Just be wary.