This is what I was doing when normal kids were playing sports and developing social skills.
In the series the reader chose to be either the Wizard or the Warrior of Good King Henry. Thus you could read each book twice and get a different story depending on the protagonist you chose. This unnamed Wizard and Warrior were best friends and general troubleshooters for said King Henry in what is probably an England that never really existed.
I would always read both versions, the Wizard and the Warrior, but my youthful inclinations were always toward the Warrior first because I had yet to appreciate the truly awesome awsemosity of the wizard in general. The cover art, at least in the American editions, tended to feature the Wizard more often than the Warrior and while I didn't get to read every book in the series, I do enjoy reviewing the covers via the magic of the internet. As often happens in a book situation the cover does not, necessarily, depict accurately what is going to happen in the pages contained within.
Which brings me to my point.
What in the hell is the Wizard doing here?
The Siege of the Dragonriders was the second book in the series and the first to feature the Wizard on the cover, the first having featured the Warrior in both the American and British editions. So the question is, what in the hell is the Wizard doing here? He's riding a dragon and shooting lightning. And the dragon seems to be breathing some rather weak looking fire. But why? I assume, having not read it, that it is simply because riding a dragon and shooting lighting is pretty badass. What's the point in being a wizard if you can't ride a dragon and shoot lightning from your fingertips?
I notice also that the Wizard in the logo is wearing green and looks much less impressive. Still, riding a dragon, shooting lightning which is never going to reach that castle, you have to ask why he's using up the badass points with no one to see him.
Just for comparison's sake, that's the British edition, featuring the Warrior fighting a dragon. Not nearly as badass, but where's our buddy the Wizard?
Off riding a dragon and shooting lightning like the cover of some 80s heavy metal album, that's where.