I've taken a couple 2-year breaks from programming - once to start a company, and another time for personal reasons. Like you, I didn't not know how the time gap itself and the reasons for it would affect my conversations with potential employers. Well, turns out it's a non-issue. I've never had a conversation about it one way or another - every employer that I've talked to only cared about my skills. In particular, I had thought that being a former startup founder would raise some red flags (would she fit in at a "desk" job etc) but like I said, it's never even come up. That's one of the perks of being a programmer I guess - if you have the skills, you have the skills.
Just out of curiosity - what is your book about?