book q: what's the deal with the Stefan diaries?

I am Lesen them. They are based on both L.J. Smith`s novels, and on the script written Von Kevin Williamson and Lulie Plec. There`s no specified writter.
I`ll let Du know that they are Mehr alike to the TV show. In fact it is the story from Stefan`s point of view only, and it begins in 1864, when he meets Katherine. All the flashbacks from the Zeigen will be there in the first book, and Mehr ;)).

somebody else writes them and stefan diaries are made from the Zeigen

+ if Du are a Damon&Katherine fan, Du are gonna Liebe the first book.