I was recommended to this link, which is a fascinating look at science fiction for young adults by Malinda Lo. In one way, it makes me feel good, because one of the reasons I started to write YA was because I thought that adventure stories, especially for boys, were underrepresented. Seems I needn't have worried.
One the flip side, I never realized I had so much excellent competition!
On the whole, though, its competition I'm glad to have, as it means the YA market for the sort of stuff I like to write, and more importantly read, is vibrant and active, and that has to be a good thing