PreS-Gr 3 When Grandmother Pig comes for a week-long visit, Amanda and her big brother Oliver have big plans for playing with her. They have to adjust, however, when it becomes clear that Grandmother isn't the show she used to be. `Grandmother is no fun,' '' Amanda claims. She can't read or sit on the floor. She thinks we are noisy. And now she is taking a nap.' '' Gram comes through, though, when Amanda has a nightmare, when Oliver gets in trouble for hiding her reading glasses, and when her solution to thunderstorm fears ends up in a pil low fight. By week's end, everyone is looking forward to the next visit. The same domestic sweetness that is pre sent in the five preceding ``Pig Family'' books is here, punctuated by mild naughtiness and some soft realism about aging and young/old relation ships. The occasional sappiness (``You are never too old for a nice nap,' said Mother'') doesn't completely overwhelm the genuine feeling and fun that also run through the story. The full-color pencil and wash illustrations with their round-headed long-eared porkies feed right into the gentle mood. If previous Pig tales move, this would be a logical additon to the beginning-to- read shelf. If you're up to your snout in sweet little family dramas, head for a sparkier trough. Nancy Palmer, The Little School, Bellevue, Wash.