My daughter loved Jacqueline Wilson as a child and she re-read this book recently.
Cliffhanger is about a boy called Tim, a very un-sporty and very un-adventurous boy who is forced to go on an adventure holiday by his dad in hope to toughen him up. Despite Tim's horror, he is forced to go there and his no-sport brain is full of sports and adventure that he has to adjust to.
The book, overall didn't impress my daughter. She told me that she didn't overly like it when she was younger anyway, however she thought that maybe it was because it was written from a boys perspective and wasn't really a book that includes the sort of plot she enjoys. However, when re-reading it she saw that the book as very bleak for her. She told me that there was no proper introduction to characters, or not even a subtle moment where you can grasp the ideas of the characters and understand whether or not you like them. In this book, the characters and your opinion of them, is already there. You kinda just have to take it. Of course you can make your own opinions but you can't take them from a new perspective.
If you're a younger reader or have a younger child who likes reading, this book would be for you. It would be nice for them to read as it's simple. Also, I think this could be used in the classroom as it's a very simple book and would teach the child the basic literary techniques.