In my career, I’ve worked a lot with rhyming picture book texts. Not on my agenting list, unfortunately, since the market for rhyming picture books was (and remains) tough. Of my dozen or so picture book author clients, most were author-illustrators who could bring a unique art voice and sense of balance between text and image, the rest were prose picture book writers, and only one worked exclusively in rhyme. Tough odds. The rhyming one did get a book deal during our work together (the absolutely charming GOODNIGHT, ARK by Laura Sassi, illustrated by Jane Chapman), but I heard over and over again from editors that rhyming was tough.
Well, let’s leave rhyming out of it and talk about rhyming’s black sheep sister for a minute: rhythm. If you want to write rhyming picture books, I would actually argue that rhythm, not rhyme, is king of the genre. Most people get so caught up in finding the right rhyme that their rhythm is all over the place and completely sinks the manuscript, almost before it gets started. Are you writing in rhyme and failing to count your syllables? Disaster lies in that direction.
The biggest mistake people writing rhyming PBs make is letting rhyme dictate story. Why does the dog have fleas? Because it has to eat cheese in order for the rhyme to work? Wrong. You’ve written yourself into a prison and you’re going to keep sacrificing the integrity of the story just to hit your rhymes. That’s not great.
The second biggest mistake, as you might be able to guess, is not paying attention to rhythm. If you aren’t yet familiar with syllable counts, iambs, trochees, and all the other trappings of verse, it may be worth your while to get a high school or college poetry textbook. That’s right. A textbook. Because there is stuff to learn about rhythm that was so intricate that you quicky repressed it in the 9th grade. People have been hammering away at poetry for centuries and centuries. Give their hard work at least a cursory nod and study the poetic form before you throw your hat in the ring.
You could have the most beautiful rhyme in the world but if the read-aloud factor isn’t there, and it’s pitted like a road after winter, with starts and stops, your rhyming picture book will go flat. And if you aren’t reading your work aloud as you compose or edit, especially for rhyming picture books, what, exactly, are you doing?! That is absolutely essential, because how it sounds in your head probably isn’t how it sounds out in the air.
Ideally you compose for content (story) and cadence (rhythm). Those two come first and foremost. Only when you master rhythm can you even think about incorporating rhyme.