Co-author?

One and a half hours into my annual appraisal meeting:
Boss: So, where do you see yourself in five to seven years?
Me: Oh, I'm a yoga teacher. Or may be I'm writing a book. I could also be the MD of a company...

As I put together the leader's toolkit and our guide for how to conduct annual appraisal meetings, the question shouldn't have come as a surprise, but somehow I was so in the moment that it did. And when I saw my boss making some notes about my aspirations I wondered how smart it was to be so honest...

Boss: Aha, writing a book. I've been thinking about that too...

So may be we will be writing a book together??