If the premise appeals, don't worry about not knowing each work mentioned in the crossover!
The author introduces each setting and character quite well, and anyway, the connection is the delightful mechanism that the interactions revolve around. If you like the idea of strange and wonderful teenagers getting to know each other and a reality that expands ever larger, give this a whirl. It made me sigh with pleasure, and still makes me vibrate with anticipation for the next chapter, and the next, and the next--