The first book is a complete story in itself. It is part of a trilogy, but having read the sequels, I can assure you that they're much weaker, which is why I won't nominate or request them. IMO the first book should've remained a standalone book.

(One of the authors died some time during writing the second or third book, and they took a different co-author on board, which could be the reason for the disconnect. Personally I ignore the sequels, which is why I didn't mention them in my promo post.)