Can you recommend some good imaginary friend horror novels?

Sure. One popular one is 'The Invisible Companion' which features a girl who has an otherworldly friend that helps her solve mysteries in her small town. It has great character development and an engaging plot.

One horror story is about a girl who had an imaginary friend named Lily. At first, Lily was just a playmate, but then things got creepy. The girl would find things moved around her room in the middle of the night. And she often heard whispers that she thought were from Lily, but the words were always menacing, like 'You're not alone here.' It was so terrifying that she finally told her parents, who then moved her to a new room, hoping to leave the 'imaginary friend' behind.

A young child had an imaginary friend named Shadow. Shadow would tell the child to do strange things like hiding in small, dark spaces for long periods. The child would come out all disheveled and with scratches that he couldn't explain. One time, the child was found in the attic, murmuring to Shadow. When his mother tried to pull him away, it was as if an unseen force was holding him back. After that incident, the family became very worried and sought help from a psychologist, thinking it was some sort of psychological issue, but the horrors related to Shadow didn't stop right away.

Once there was a little girl named Lily who had an imaginary friend named Charlie. At first, Charlie was fun, but then strange things started to happen. Lily would wake up with scratches on her arms, and she'd hear Charlie whispering dark things at night. One day, she saw Charlie's shadow, which was distorted and menacing. It seemed like Charlie wasn't a friendly imaginary friend anymore but something evil that wanted to harm her. Eventually, Lily's parents noticed her distress and moved her to a new house. Since then, she never saw Charlie again.

Often, these imaginary friends in horror novels are not what they seem. They might start off as something innocent but then turn into something malevolent. For example, in some novels, the imaginary friend starts to manipulate the child or the person who believes in it, making them do things that are harmful or against their will. This transformation from something seemingly harmless to something truly evil is a big part of what makes these novels terrifying. It plays on our fear of the unknown and the things that lurk in the shadows of our minds. Also, it can be related to our childhood fears of things that go bump in the night and the monsters under the bed, but in a more psychological and insidious way.

One common element is the sudden change in the imaginary friend's behavior. For example, it might start as friendly but turn malevolent over time. Another is that the main character often has no one to believe them when they try to tell others about the scary things the imaginary friend is doing. And often, there are signs of physical harm or strange occurrences associated with the imaginary friend, like objects moving on their own or unexplained scratches.

One good example is 'The Lovely Bones' by Alice Sebold. In the novel, the main character who has passed away acts as an 'imaginary friend' of sorts to those she left behind. She observes their lives and her presence has a profound impact on them.

One heartwarming story is about a boy and his imaginary friend, a tiny elf. The elf would help the boy with his homework by magically showing him the right answers. Of course, it was really the boy using his own knowledge but believing the elf was helping. When the boy was sick, the elf would bring him 'healing' leaves. It was a special bond that made the boy feel loved and cared for.

One creepy story is about a girl who had an imaginary friend named Lucy. Lucy always told the girl to do dangerous things like climb on the roof. One day, the girl almost fell while following Lucy's advice. Another time, Lucy made the girl lock herself in a dark closet for hours. It was really terrifying for the girl's parents when they finally found out what was going on.

The unknown nature of these 'friends' is terrifying. They can be shadowy figures or just voices, and you don't really know where they come from or what they are capable of. In some stories, they seem to have powers that are used to frighten the children, like moving things around or making strange noises that you can't explain.