This is the Social Register, or just plain "the register." Over the years the number of entries have grown...it's now pretty thick compared to decades ago. It's the list of lots of nice people all over, including where they summer, contact info, clubs, et al. You get two of them a year, with updates included.
In my mother and grandmother's day, it meant everything. My Mimi used it like the phone book. Engagement, wedding and death notices were published there (as Mimi used to say, "A lady should appear in print thrice in her lifetime: birth, marriage and death"). Today, not so much...one can disappear from the listings if one doesn't send in one's info...and I certainly can't imagine limiting my sphere of friendships to the book. Basically, it's still a pleasant diversion and a retro "nice-to-have." Mine sits on a table in the den, a reminder of those more gracious times.