Ever since Harry had come home for the summer holidays, Uncle Vernon had been treating him like a bomb that might go off at any moment, because Harry Potter wasn't a normal boy. As a matter of fact, he was as not normal as it is possible to be.
{Ever since|Since} Harry had come {home|back} for the {summer holidays|summer break}, Uncle Vernon had been treating him like {a bomb|an explosive device} that might go off at any moment, because Harry Potter {wasn't|was not} a {normal|typical} boy. {As a matter of fact|In fact}, he {was as not normal as it is possible to be|could not be more abnormal}.