Have you written any other novels in collaboration with other writers?
Why, yes. Several times, as a matter of fact.
The first was when during my days at Shooting Star Comics when John Morgan Neal and I collaborated on the first crossover between characters in the SSC anthology. We worked together to establish a starting, cut-off, and ending point, then I wrote the opening chapter, and he wrote the closing one. Two parts. That's all. Easy peasy.
The next time was more in the creation of the character. Bobby Nash and I met over dinner to flesh out the story bible for a character we created together for Airship 27 -- Rick Ruby (The Ruby Files). We didn't actually craft any stories together during that one though, just the main overall story for the characters that should be reflected and kept in mind for all stories written in Rick Ruby's world.
The most recent has been my collaborations with my new comic book writing partner, Ashton Adams. We initially started working in one way (I write the plots, then he turns them into scripts), but we've recently begun plotting and creating together, then having him do the actually scripting for the most part and me putting the "polish" on them.
But as you can tell, each time is a different animal.