He didn’t write his “autobiographies”.
We don’t know, but I’ve read the Audacity of Hope, and it definitely felt like something Obama would write. It’s hard to imagine some ghostwriter managing to impart such intensity of self admiration without thinking “christ, I should tone this down a bit”. Also, it’s written in a way that FEELS like Obama - all these precious little turns of phrase - you can imagine the guy nodding in that self-satisfied way of his when he wrote those bits. Totally bereft of content or emotional depth; undergrad creative writing stuff. If Ayers or someone wrote it he is a hell of a ghostwriter.