Alexa and I started tagging on 'Room at the Edge', the sequel to 'Room at the Top' yesterday.
People sometimes ask how co-writing works; for us, it's really trouble free. We draft out a plot via email, open a Google doc and start to tag, trading paragraphs back and forth. The tags can be a couple of lines or a couple of hundred words, depending.
Back when we started to write together, we'd each pick a character and be the only one to write them, but that, though it was good in that it gave the characters a distinct voice, got cumbersome. We started to borrow each others character for a few lines, then more, and things got faster.
Now, we tend to dream up a character each, choose their eye color, hair, characteristics and such, but after creating a character bible, we both write them.
Co-writing is fast. Alone, I struggle to do a thousand words a day, staring blankly at an equally blank screen; tagging, we can do 5,000 a day without any difficulty.
I'd never give up solo writing, but there's no denying that co-writing is a breeze.
Of course, that's because I've got Alexa on the other end of the tag and she rocks :-)