Authors Redfern and Roberts have done a masterful job of compiling government files, both British and American, about everything from UFOs to Spontaneous Human Combustion, shedding much light on what there governments really know (at least, based on files that were released to the public). Though some mysteries are solved or, at least, given plausible explanations, others still remain up in the air (so to speak).
The book could have benefitted a little by being fleshed out with outside material. The chapter on Men in Black is intriguing, but ultimately leaves some nagging questions. And a few case histories from medical literature could have helped the chapter on spontaneous human combustion. The section on UFOs is well done, but those looking for insights into Roswell, MJ-12, or the Rendlesham/Bentwaters incident will find nothing here (though, in all fairness, each of those topics have been the subject of numerous books of their own).
Despite these caveats, and the fact that this book will be disappointing to the hardcore conspiracy buff (who will, no doubt, distrust just about anything the government says), this book is highly recommended for those looking for solid answers based on genuine research and solid reasoning.