The world is full of unexplained mysteries – unusual events that nobody can understand, and questions that nobody can answer. Do UFOs exist? Is there life on other planets? Why do some people go missing without a trace? This book explores some of the most intriguing mysteries over the years, and the theories that people have developed to explain them. Sapphire level titles provide a selection of stories and non-fiction titles chosen for their range of content, narrative and points of view. This level encourages readers to form opinions and discuss their own reading tastes. PM Guided Reading Non-fiction books are fascinating texts that increase in word count and pages in line with progression of children’s reading age, for appropriate literacy skills development. The books represent all the standard text types and contain literal, inferential and applied knowledge questions to test comprehension and promote discussion. #pm19-offer