Here's the whole idea: each of these is book one of a series a child can fall into, so you're not looking for the perfect next read, you're looking for the one that grabs them. Hand over the one that fits their kind of fun, and if it clicks, the rest of that series is right behind it. Try one, and you might have just bought yourself a year of bedtimes.
These aren't rungs on a ladder, they're six doors into six different kinds of fun, and every one is the first of a series. A silly pig, a half-fairy half-vampire girl, a girl scientist who helps dragons, the world's crankiest cat, a monster chase, a baseball whodunit. You're not working through them in order and you're not building toward anything, you're finding the one that grabs your child. The moment one does, the win isn't finishing this shelf, it's that a whole series is waiting behind whichever book they loved. Pick by what makes your child light up, not by where it sits on the page.