Without a doubt get it. I have read it and reread it many times. Each time I pick up something new. The Super Ultralight Chapter is worth the price of the book alone.
Also you should consider getting Lighten Up if you dont already have it. Actually I would recommend you read it first.
Another nice to have it Trail Life by Ray Jardine.
I have other lightweight books but have not found them to really add anything that these 3 do not already cover.