Usborne The World of the Unknown - All About Monsters
Printed in 1977 the book has that "In Search of..." feel to it and tried to cover as many varied aspects of Monster-dom as it could at a meager 32 pages. The Illustrations were spectacular and held my fascination for hours. Just look at that cover screaming 70's obsession with the Loch Ness Monster...
Usborne The World of the Unknown - All About Ghosts
Again 32 pages but covering a variety of topics relating to ghosts, including haunts from folklore and literature, to real-life hauntings from the modern era, and even methods for creating a hoax.
Check out the detailed "Haunted House"
Usborne The World of the Unknown - All About UFOs
Again another 32 page illustration laden masterpiece whose subject matter was seemed particularly riveting to my Dad back in the 70's. He watched "In Search of.." all the time, had a Moa statue, watched documentaries on Ancient Astronauts whenever they were on television (that and Hammer Dracula movies) so this book was a must have.
Awwww now I need to go find these books for my daughter