Starting 5th grade at Beecher Prep, Auggie wants nothing more than to be treated as an ordinary kid - but his new classmates can't get past his extraordinary face. Wonder begins from Auggie's point of view, but soon switches to include the perspectives of his classmates, his sister, her boyfriend, and others.

Wrth i Auggie fynd i'r ysgol am y tro cyntaf yn 10 oed, mae e'n ysu am gael ei drin fel unrhyw blentyn arall mewn ysgol Americanaidd. Ond dydy'r plant eraill yn ei ddosbarth newydd ddim yn gallu gweld heibio i'w wyneb rhyfeddol, sy'n ennyn ymateb cas, caredig a chymhleth fel ei gilydd.