This is one of those picture books that nails a specific developmental moment. If you're dealing with sibling rivalry or preparing for a new baby, Julius is gold—it's honest without being preachy, funny without minimizing real feelings, and short enough to read multiple times when your kid needs the message to sink in.

Henkes doesn't pretend that kids instantly love their siblings. Lilly is bratty and mean, and the book lets her be that way until she has her own realization. Parents love it because it opens up conversations about jealousy that kids might not know how to start themselves.

The one caveat: there's a brief mention of babies growing inside mothers, which Common Sense Media flags. It's not graphic, but if you're not ready for that conversation, heads up.

Overall, it's a classic for a reason—emotionally smart, developmentally appropriate, and genuinely useful for families in the thick of sibling dynamics.