I made it clear from the very first moment that I was collecting stories for a book and asked permission from every contributor to confirm they knew it was for a book. I also sent them regular updates about the book and when it was published.
Just very honest and transparent about the process and what I was trying to do. And after the first one came out, I had more people sending me stories unsolicited and understood the book already and I’d often send them a free digital copy of the first one to really see what I was doing and what they were agreeing to.
The contributors have all had very positive reactions to the book (of those who responded/reached out).