Jeff Mariotte explained why the stories do not reference each other:
We didn't get to read each other's stories, we just knew a tiny bit about what would happen in the ones before and after ours. So, for instance, I mentioned in the very end of mine that Angel knew he had to go do some last-minute shopping. But we knew it wouldn't flow exactly right, because if it did then it would be a novel by a buncha different writers, and not a collection of short stories.
The book is unique, the only anthology of Angel short stories. The book is labeled 'Vol. 1', suggesting further volumes were a possibility, but none were ever released.