Invisibill by Maureen Fergus
Bill just wanted someone to pass him the potatoes. Unfortunately, no one even noticed--not his mother (a very busy woman with an important job), not his father (a very important man with a busy job), not his very intelligent older brother, not even his very athletic little sister. If someone had noticed, the wonderful, terrible thing that happened might never have happened. But it did. InvisiBill is the hilariously absurd, tongue-in-cheek story of an ordinary middle child who feels so overlooked by his busy, distracted family that he becomes invisible ... or InvisiBill!