Stephanie Books
(Book titles)

General
Full House Stephanie/Club Stephanie Started around the beginning of season 7 with "Phone Call From a Flamingo." The Flamingoes are a snobby, mean-spirited clique in Stephanie's school, John Muir Middle School. (Yes, that's different than in the show.) While the Flamingoes weren't mentioned in every book of the Stephanie series, they branched off into their own, called Club Stephanie.
Now, it seems they've gone totally toward Club Stephanie and away from just Stephanie, and have it geared more toward Stephanie in 9th grade, which would be a 10th season. These focus more on their battles over guys and stuff, and a number of Club Stephanie books
Differences with tv series
There is one thing you will notice in the book series, which has a point of departure before the TV series takes place. In the Full House Stephanie book "Here Comes the Brand New Me," which takes place at the start of TV season 8, Michelle is already eight years old. A summer birthday is maintained throughout the books except for one. This is to make it more realistic - Michelle started Kindregarten in the TV series over two months before she turned five. By turning back her birthday to summer - arguably, late spring - it's much more realistic. Same with Joey's apartment in the basement.

The Stephanie book series introduce 2 new character: Allie Taylor and Darcy Powell. And, using Allie makes sense in a way. Stephanie has been friends with Allie since Kindergarten, the books say. Well, we rarely see Stephane's friends in the series. So, it makes sense to introduce others.
Allie could easily be in the series, in fact. One girl we see on TV several times, while unnamed, does remind one of Allie. Look at the third episode of the series ("The First Day of School"). One can imagine it's Allie in a different hairdo who we glimpse running away screaming, with her mom chasing her and trying to get her to go into the school building. Allie is very shy around boys. She could have been extremely shy, period, early in her life. A couple other episodes have girls who look like they could be Allie, including "Crushed."