Dark Lord #2: School's Out by Jamie Thomson

This book is the second in the series. Dirk Lloyd is actually the Dark Lord of the Darklands, but he's been trapped in the body of a human boy by Lord Hasdruban. Christopher and Sooz are his friends, but Sooz mistakenly gets sent to the Darklands. It's not easy to travel between worlds, so she's on her own. She is wearing the Dark Lord's ring, so his followers think she's going to be their queen. This keeps her alive for awhile, but the Dark Lord's enemies are preparing to attack. Meanwhile, Dirk, the Dark Lord, is stuck back on Earth trying to figure out how to help Sooz. Lord Hasdruban sends an assassin to kill Dirk which complicates things a little. Dirk doesn't have the power to travel back to the Dark Lands, and Sooz doesn't know what she's doing. Can they both survive?

I didn't read the first book in the series, but I was able to easily understand what was going on. You'll figure out pretty quickly that Dirk isn't as evil as people think he is, and his enemies in the Dark Lands aren't all that good. It's funny listening to him help people while he's trying to be evil. Sooz rules the Dark Lands differently than Dirk which makes things interesting. His evil followers aren't sure how to react to Sooz's kind ways, and it's even more confusing when Dirk returns. The first book in the series is called Dark Lord: The Early Years.