Hey, yellow-sub! I just turned in a "stand-alone companion book" on Monday, the second that I've done. But it was writing under contract that I found way more stressful than the fact that it was a follow-up book. What are you finding the most difficult? Since I was writing fantasy, it was a relief in some ways that I'd already done so much of the work of creating the world and now I could focus other things. You know, like plot and character!