He's been a hard hitting liberal for years, but raises excellent points that can help his home state of Michigan.
I've read about 4 of his books, he is highly entertaining, and explains things very well. He is also right more often than wrong. Ben and Me was his first scathing hit at the auto industry that destroyed his hometown of Flint, Michigan. Our heathcare is ****, always has been, and still is. He has a great book about it as well as Sicko, his documentary. He also laid out an excellent reveal of politics in his book Stupid White Men.
My biggest problem with Moore, is during the second Bush election, when people were looking for change, he held these huge speaking engagements in swing states. Undecideds genuinely wanted to listen to what he had to say, but he started frothing at the mouth, and putting down conservative culture. Hundreds of people walked out, so he ended up only speaking to his base. It looks like he's doing a much better job at getting his point across, while not attacking the people specifically.