In many ways Shriver was a remarkable man. He, more than anyone, could claim to have had more fingers more "liberal pies" than anyone in the American politics of the 1960s.
That said he was also hideously disorganised (getting by on passion, drive and intelligence) than any other subject of a political biography that I've read.
When his disorganisation is coupled with shabby treatment at the hands of his in-laws (as an example, Ted Kennedy would only refer to him as "Eunice's husband" in a stump speech to avoid saying his name), his general "niceness," and lack of "political killer instinct," it's probably not surprising he didn't achieve all he could politically.
That said, it's a good book, you'll just finish it wondering "What if...?"