I'm interested to hear whether you'd literally move over to Ruby (exclusively Rails?) or just use it as another tool in your tool-belt alongside PHP. Personally, I think the former would be a silly thing to do.

Take the time to get to know Rails, and Ruby, as it's always good to see how things are done better, worse or just differently based on your own experience and learning. However, I wouldn't advise jumping ship entirely based on a book.