Why are Jehovah's Witnesses considered a cult?!?

I know about five Jehovah's Witnesses, they are devout but really normal people. They watch the same movies and wear the same clothes and break a rule sometimes but they are pretty religious. I know books like The Room make Jehovah's Witnesses look like a cult, but have you ever thoguht maybe the boys mother was just a psycho?? (read the description of the book) I've even been to a Kingdom Hall and it seems very similar to church.