My favorite series as a child was the Red Bicycle series, which started out as exciting urban fantasy Christian propaganda with magical bicycles and varyingly dubious morals (video games are bad for you! popularity contests in school are bad for you! be nice to your siblings, even the annoying ones! adults probably don't understand the mystical battle between good and evil going on in your town!), which got weirder and weirder as the series went on. And then darker and darker, as the author decided to stop pulling from modern life and cue up the book of Revelation. It went sort of...The Last Battle, really.

I also remember being passionately invested in whether the Black Stallion or his son, Satan, could actually win in a race between the two of them, and disappointed that the answer was carefully left ambiguous.

And now I desperately want to track down the Henry Reed stories again. (Not so much the Mad Scientists Club series, which was fun but kinda forgettable.) Were there more than two books in the series? My library only had the two.