I've seen some book websites (and sometimes published books) with kits for book clubs—everything from discussion questions to activities to refreshment ideas. What makes for a "good" book club kit?
Having book club questions as part of the printed book is becoming very popular. You're more likely to find/need to provide these questions for women's books and Middle Grade/YAs. Discussion questions depend on the type of book and should be more than just a book content trivia quiz.
Personally, I like questions that relate things that happen in the book to the reader's real life.
From a book club perspective, get some ideas HERE and HERE and HERE. You'll want to customize them for your book.
As far as a book club kit, the more you provide, the better. You could do themed party ideas and provide suggestions for anything from decorations and invitations, to games and other activities, to refreshments and door prize ideas—your imagination is the limit.
Is this necessary? No. But as someone who attends a couple of book clubs and often finds them tedious, it is lots of fun to turn it into a party. (Which I do when it's my turn to host.)