GI (Glycemic Index) Diet???

Is anyone familiar with the GI diet or used it before? I've heard the name so many times and found this book by Rick Gallop on sale for dirt cheap so thought I'd give it a read. But like most diet trends, I'm wondering if this will work for a while and then be one of those things where all the weight comes back fast. I'm not a diet trend kinda person but only 13lbs in and I think I've hit a little bit of a plateau. Changed my exercise and still no change. Sooo, maybe I need to change up my foods.