The title suggests that this will be a (very) broad comedy. However, it is written with considerably more wit and precision than I expected.
The problem with books of this type (for readers outside the US) is that we are not that familiar with subject matter - I have no real opinion about whether the US media has a liberal bias although if the UK media is anything to go by it seems very unlikely.
Franken states that the primary of objective of the book is to be funny; he succeeds admirably although he does on occasion descend into pettiness and name calling. I certainly laughed hard and often as I read the book.
There are some very good chapters in this book. For example, you get a good sense of Franken's heart felt indignation in the chapter about Paul Wellstone's funeral; the exposure of push poll tactics is horrifying, the chapter on how Fox News makes you stupid is hilarious; Karl Rove, Sean Hannity and Bill O'Reilly come in for the kickings that they richly deserve.
On the negative side: for me, his unconditional love of Bill Clinton got a bit too much at times and he is guilty of constantly criticising the conservative agenda while not really discussing the issues with the liberal agenda. However, these are minor quibbles; they did not detract from my enjoyment.
I think that the comparisons to Michael Moore are slightly unkind to Franken. Overall, he has less of an agenda than Moore who I regard as a polemicist, he is funnier and more precise; it is like comparing a scalpel to a sledgehammer.
Very funny, highly recommended particularly if you have a strong interest in US politics