Both Arthur and his little sister D.W. are featured in two new titles. In D.W. Rides Again! (ISBN: 0-316-11356-5), baby Kate gets the trike while Arthur is all condescending big brother in detailing safety rules for D.W., who's learning how to ride her bike without training wheels: a useful summary whose didacticism is nicely defused by its good humor. In Arthur's New Puppy, the tables are turned: now it's D.W. who comes up with comically sensible comments as Arthur learns to cope with his lively new pet (```Look, he's so excited,' said Arthur. `Look at your pants,' said D.W. `You have excitement all over them'''). For a while it's not clear whether Pal is ``just a baby'' or a ``problem puppy,'' but after a suitable amount of comic mayhem, the equable aardvark family's good sense prevails once again. An appealing pair. (Picture book. 4-8)