This book is fairly typical of the things I liked to read when I was a child: a purported series of “facts” about monsters, mythical and real (and some created by Hollywood). There’s color illustrations, and probably less than 1000 words of text, total. Various categories overlap – although “Giants” get their own page, the Cyclops there would fit as easily into “Mammoth Monsters” or “Mythical Monsters,” while most of the “Monsters of the Sky” are also mythical. The description of “Werewolves” is based on Hollywood lore – before the movies no werewolf got stuck in half-human form, they always transformed fully into wolves. Still, it was good fun for a kid that hadn’t yet discovered “The Monster Manual.”
This is a good introductory book for kids, giving a tiny bit of info on many different "monsters". It is an older book, so I am sure there are more options now a days.