This is a pretty broad cross section of mysteries throughout history, from the relatively mundane (did Shakespeare actually write his own plays? Did Hitler die in his bunker?), to the outlandish (chupacabras, UFOs). A fair number are ones you might already be familiar with (the Dyatlov Pass incident, Mothman, the aforementioned chupacabras), but I did find several strange incidents I'd never heard of before, like the Faces of Belmez, and the Isdal Woman.
However, for all its breadth, Unsolved Enigmas has sacrificed depth. In the introduction, Pilger writes that this isn't a book about searching for answers, but appreciating the mysteries for what they are. Which feels...if not lazy, then at least a bit lacking, to me. Still, if you're looking for an entertaining diversion, or a surface-level introduction to some bizarre rabbit holes, it's a decent enough book.