What is dream?

Joris Sharpe (pseudonym of Joris van Leeuwen 1986) has written many books alone and in combination with other writers.
I read the pre-published version of Syndrome and I'm puzzled.
Peter (21 years old) is living with his father (writer with writers block) and sister (Aisha 10 years younger) after his mother had an accident and is in coma. When he picks his sister up from school and goes to the mall to buy some cloths they're being chased by a strange car with a much stranger driver. Peter convinces himself that it is because of the rain that it all looks strange but then his sister vanishes and he needs to find her. The strange thing is that nobody has seen his sister with him and even his father and friends denying the fact that he has a sister. What is going on? Is he in a sick tv-pranck or???
Directly from the beginning the book grabs you and doesn't let go until the end. You don't have any problems with feeling the confusion, anxiety or anger Peter feels. As a reader you're in a constant puzzled state like Peter.
The book lets you read from 3 points of view. First and most of the book it is Peter telling his story, his feelings, his search for his sister and trying to find out what is dream and what is reality.
There are also some chapters for Emma, mother of Peter and Aisha and at the end of the book are some chapters for Hannah, friend of Peter and his family.
The character Peter has been build up very good, the other characters a little less but that is no problem in this story.
The suspense is built up from the beginning and the few chapters with Emma gives the reader a little pause to release the shivers.
The plot is also built up with many twists and it ends different from what you would imagine. That is also the reason why I'm puzzled.
Why Joris?? Why did you give Syndrome this ending?? It is an amazing ending but I don't like it at all. But yeh, who am I?
Conclusion is that Syndrome is a amazing book perfect for the advanced suspense readers.