As explained in this year's Rules / Mode of Play post, we're going to reveal the seven final holidays included in the card and the respective book tasks early on, so as to allow enough time to complete these books.
The final holidays and book tasks are:
Winter Solstice / Yuletide (December 21): Read any book that takes place in December OR with ice or snow on the cover OR that revolves around the (summer or winter) equinox OR a collection of poetry by Hafez.
Festivus (December 23): Read any comedy, parody, or satire.
Christmas (December 25): Read any Christmas book.
Kwanzaa (December 26 - January 1): Read a book set in Africa or the Caribbean OR by an African, Caribbean, or African-American author OR a book with a green, red, or black cover.
New Year's Eve (December 31): Read a book about endings, new starts, or books where things go BOOM!
Hogswatch (December 32)*: Read anything by Terry Pratchett.
Epiphany (January 6): Read a book with three main characters OR a book about traveling on a journey to a faraway place OR a book that’s part of a trilogy OR with a star on the cover OR with the word “twelve” or “night” in the title OR or concerning kings or spices.
The non-book tasks for these seven holidays will be revealed on December 16, which is when we'll also be opening the corresponding doors on the calendar. (Hey, we want to keep some element of suspense at least for these ...)
* Discworld calendar.