I did the audiobook. There is quite a bit of science jargon in a lot of places, so sometimes I missed out on absorbing that well by not seeing the letters. But I am a visual learner mostly anyway for that type of stuff. But I got the big picture and it was very fascinating. Was my morning commute audiobook for a few weeks.

"I contain multitudes" by Ed Yong is also a great book on the subject. It does get pretty heavy but summarizes the big picture of our evolution with microbes. He often compares the microbiome to a new frontier.

Here's a good synopsis of the book https://www.theguardian.com/science/occams-corner/2016/aug/25/lifes-little-surprises-i-contain-multitudes-ed-yong