The best-selling book is really hard on Sarah Palin, but she did help McCain since it energized the base (certainly energized me) even if he made a questionable choice in terms of picking someone who should be VP.
The choice was a good one from the perspective that it further pushes the Republican party to the pro-life position. Republicans who are politically astute now see what pro-life Palin did for the ticket - it gave it life and money & zest. The very act of picking a pro-lifer as VP by McCain was self-fulfilling in the sense that perceptions are often reality in politics, and the perception taken from the '08 campaign: Rudy went nowhere and McCain picked a pro-life running mate instead of Lieberman. That speaks volumes.
McCain didn't lose by much and he lost mostly because of the financial crisis and his ridiculous response to it, and NOT because of Palin's disastrous interview w Couric.