The hard work

I've been busy going over and over details in my book, and I'm at the stage where I've identified the section in the book that needs the most serious re-writes and additions/removals. This is going to be some hard work.

What's also going to be hard is deciding what my next project will be. Do I move on to book 2 of this series, hoping that it'll give more weight to trying to sell the first, or move on to a different book entirely and go for variety?

Or do I take the third option, and do both?