Article body copy One of the biggest mistakes novice children’s book writers make is to assume that a story must teach something. An overt message—share, don’t be a bully, eat your veggies—can make for a boring book. There can, of course, be a lot to learn in children’s books, but it takes a deft hand to avoid being didactic. Several of this season’s marine-themed books tackle big subjects—death, extinction, fear, even a lost toy (a monumental disaster for some). But in the hands of these...