Giff is a new author who has a way with one-liners and a sense of what's comical to kids; both, she sometimes overextends (Fourth Grade Celebrity, The Girl Who Knew It All, both p. 215, J-57); but with second-grader Ronald Morgan's truly terrible day--and the gaffe-a-page easy-reader format--she's in her element. Ronald's first misstep, when he notices that his mother has forgotten to sign his homework, is to sign it for her (""so she wouldn't get in trouble""); but, says teacher Miss Tyler, ""It is a crime to sign other people's names. And you spelled your mother's name wrong."" Naturally: ""all the children laughed."" There are other foul-ups--like a sneaked sandwich that turns out to be someone else's (""And Jimmy cried because he didn't want my sandwich"")--but back of all Ronald's trouble is something we learn (naturally, too) from a loudmouthed classmate; ""He still can't read."" No hand-wringing follows; but at the end of that terrible day Miss Tyler gives Ronald a note to take home, with the suggestion that he try to read it. Smart Miss Tyler! The note--which of course Ronald does read--is addressed to him and says ""I'm sorry you had a sad day""; tomorrow, she promises, will be a happy one. With sympathetically funny pictures by Susanna Natti, a book precisely--and lightly--aimed at second graders struggling to break through into reading.