Based on grade level, the word book list vocabulary most common for that particular grade. So if your protagonist is in the 5th grade, the book can guide you to the words s/he would know at that level. Included in the word book is also a thesaurus. Have a specific word in mind, this book shows you the like words and what level that like word falls under.
So while the Children's Writer's Word Book can't solve the whole trouble of character speech, it certainly can help.
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