Draculaura and the New Stepmomster is the first book in the Monster High Diaries book series.
Draculaura is delighted to learn that her father is getting married to Ramoanah, a vampire he met during his recent trip to Antartica, gaining Draculaura a new stepmother. The wedding is to be held in Transylvania, and Draculaura invites Frankie, Clawdeen, Cleo and Ghoulia to join her. Draculaura is excited to meet Ramoanah, hoping that she'll be good friends with her, and get to be her maid of horror.
The ghouls travel to Chateau Transylvania, the fanciest hotel in Transylvania, where they run into Elissabat, who has also been invited, and is being filmed by a reality show documenting her life as the Vampire Queen. Fangsley, the head butler, leads the ghouls to a small party being held by Ramoanah's family. Draculaura finally meets Ramoanah, but she acts very coldly toward her, and the rest of the family, particularly Ramoanah's mother, aren't pleased to see Draculaura's friends.
Things don't improve much when they attend dinner. Not only are Draculaura and her friends placed in a separate table away from her father, but the food is all blood-filled vampire meals, which none of the ghouls can stomach. Draculaura explains to Ramoanah that she is a vegetarian, which seems to anger Ramoanah. Afterwards, Draculaura and Elissabat teach their friends how to waltz and join in on a large dance, which cheers her up for a while. But then she overhears Ramoanah having an argument with her mother, in which she mentions that she doesn't want Draculaura to discover something.
The next morning, the ghouls suggest that Draculaura should invite Ramoanah to join her at the hotel spa, so they can get to know each other better. She finds Ramoanah having breakfast with Dracula and her relatives. There she meets Ramoanah's nephew Alexander, a rather rude vampire who was asked to escort her at the wedding, and isn't pleased about it. Draculaura is delighted when Ramoanah says she can be her maid of horror, but is let down when she reveals there's not much left for her to help with. Convinced Ramoanah hates her, Draculaura rejoins her friends and laments than she feels she's being pushed out of her own family. Her friends suggest that she talk to her father about it, especially since Ramoanah appears to be hiding something.
Draculaura talks to her father and expresses her concerns that Ramoanah doesn't like her. Dracula explains that she genuinely is trying to be friends with her. While she may seem cold, its because she's lived among traditional vampires her whole life, and is still unused to opening up to others outside of her family. Draculaura decides to give her another chance. She returns to her room to discover someone has given her friends some meals they can actually eat... and that her friends have gone somewhere with Ramoanah. Hours pass with no sign of them, so she decides to hang out with Elissabat. They run into Alexander, who mocks Draculaura for being friends with non-vampires and refuses to escort her at the wedding. Draculaura is hurt by the comment, and she becomes even more confused when her friends return, claiming that they were helping Ramoanah with something, and they consider her a friend.
The day of the wedding finally comes, but Draculaura is unable to muster any enthusiasm. As she and her father enter the castle where the wedding is held, Ramoanah meets them and apologizes to Draculaura for not being more welcoming, and that she truly wants to change her ways and be more accepting like Draculaura and her father. She explains that she was angry at the dinner because the hotel hadn't arranged for proper meals for Draculaura and her friends, and has been working to rectify it in time for the wedding, with help from the other ghouls. She was the one who sent the ghouls their favourite foods. She then reveals the secret she was hiding.... it's none other that Clawd, who she arranged to come over on a first class ticket. Draculaura is delighted, and promises that she'll help Ramoanah become more accustomed to her new life with Dracula.
The story ends with Draculaura describing the wedding and the party afterwards, which all went splendidly, and how she can't wait to spend more time with Ramoanah.
The story references the events of Frights, Camera, Action!, indicating it takes place some time after the movie.