I was excited about getting a sneak preview of “Joy” because director David O Russell’s last few movies (“The Fighter,” “Silver Linings Playbook” and “American Hustle”) have been so entertaining. I wish I could say the same about “Joy.”

Jennifer Lawrence is terrific as the real-life Joy Mangano, a divorced, working-class mother who invented the Miracle Mop and sold her product with great success on the Home Shopping Network. Lawrence leads a cast that includes David O Russell favorites, Robert De Niro and Bradley Cooper, along with Virginia Madsen, Isabella Rossellini and Diane Ladd. The problem with the movie isn’t the actors. It’s the kitchen-sink approach to telling Joy’s story. The first half has a wonderful manic energy and I loved it. We learn that Joy’s divorced but her ex lives in the basement of her house and is still her buddy; that her father’s latest girlfriend is a wealthy widow who ends up backing Joy’s mop; that her mom hides in her bedroom watching soap operas (fun cameos by Susan Lucci and Donna Mills); and that her grandmother has always been her biggest champion, telling her she can do anything she puts her mind to.

It’s the second half of the movie that falls apart. The pace slows to a crawl at times, particularly when Joy gets to HSN. We watch her succeed, lose everything, sink to rock bottom, recover, become a mogul – and none of it makes a lot of sense. The tone veers wildly from girl-makes-good story to total farce, and the editing is choppy. Worst of all, it seems to take forever for “The End” to appear on the screen. “Joy” isn’t a bad movie by any means. It’s just not what I’ve come to expect from a good director. I loved that he chose to tell the story of a female protagonist, but I wondered throughout the movie why he picked this one. It’s just not that interesting.