I've settled on doing a book on subjective reality. I'll probably draft a proposal for it next week. I imagine Hay House will like the topic since they already published a very short book with similar slant -- Lucid Living by Tim Freke.
Part of the reason I opted for subjective reality is that the topic is very suitable for the medium of plain text. It's the kind of topic that takes a while to sink in, so people can pause as they read and think about it. It also doesn't require expressing a lot of emotion.
I think polarity would work better as an audio or video program vs. a book.