Well, the 2014 holiday special comic is not canon because despite the story having to be set after Rainbow Rocks, it treats Sunset Shimmer’s sleepover at Pinkie Pie’s house as her first and in Rarity’s house as Sunset’s second despite her having one in Rainbow Rocks. Also, the comic also showed that Sunset lived in the library of CHS. But in the Summertime Short, “Monday Blues”, we discovered that Sunset has a house of her very own.
This was made under the impression that then unknown holiday special would be an adaptation of this comic.
It wasn’t
Edited
Literally every one of the Equestria Girls books was written based on the scripts for the specials.
And the script for the special was written first
But technically, the book came out before the special aired.
That there is nothing to suggest it’s a Christmas special at this point, or remotely connected to this comic.
No, other way around - the book was based on Forgotten Friendship.
No it wasn’t

your current filter.Edited
That’s not true, Forgotten Friendship was based on a book.