If you find it crumbly, all you have to do is boil it longer in the microwave.
These tasted great but were too crumbly to hold together even after pressing them very hard into the pan.
The kids loved these. DH and I thought them to be too sweet. I used butter instead of margarine, but otherwise followed the recipe. I think we were expecting them to be more like Rice Krispy treats. The addition of some melted marshmallows would probably be very good and help to hold it together more. This recipe makes a huge batch, even for my big family. Made and reviewed for PAC Fall 2008.