how many people are you in the bookclub? do you meet in person or only online? if you meet in person maybe you could talk to this person privately and tell them that the “spoilers” aren’t helping you enjoying the reading? or if you have a set of rules maybe add something like “no talking about the book before the meeting”

i get that this person might want to share their excitement or frustration with you guys…but they should be able to wait until you meet to do so