In a nutshell: A surplus of self entitled rich people, the setting a remote and eerie Irish island (the destination wedding for handsome Will and beautiful Julia) plus a plethora of stereotyped school bullies now in their late 30's. What's not to like? Well, there's a bit not to engage you at first but...it grows on you. There are a few characters I liked very much and wish their stories had continued.
This book is very similar to her previous novel The Hunting Party. There are quite a few characters in this novel and multiple points of view; I found myself intrigued by the back stories and wondered who would end up murdered. I hoped for one of the shallow creeps but no spoilers from me here.
In addition to the remote location, one which requires a boat to access, there is an old ghostly cemetery and peat bogs which can (and do) pull a person in just as quicksand would. Lots of danger, secrets and suspects.
The setting is very well described and you can picture the crashing waves against the shore, feel the cold winds and imagine the insidious bogs which nearly claimed one wedding guest.
I will read more by Lucy Foley but I have to say that The Hunting Party was a better book, in my opinion. Again, it's a similar template to her previous book but by the end of The Guest List, it was hard to have empathy for many of the characters. For what it's worth, I liked Hannah and Olivia very much so if you read this one, let me know your thoughts on the major players.
Also, last but not least, I personally did not figure out the murderer's identity until it was revealed. I saw a few reviews where the reader stated they did but I was not one of those :-)