I recently picked up Philip Nel’s 2012 dual biography of ­children’s literature luminaries, Crockett Johnson and Ruth Krauss: How an Unlikely Couple Found Love, Dodged the FBI, and Transformed ­Child­ren’s Literature, and was immediately riveted. Nel did amazing due diligence: eighty interviews! Nearly six hundred (unobtrusive) footnotes! Research at three dozen archives! All his work paid off handsomely.