I am constantly searching for a single, compact reference book that covers the majority of the information that I need in day-to-day work. I haven't found one yet and probably never will. This book is very comprehensive (at 3.5 cm thick it would need a very big "pocket") and appears to have chosen to concentrate on more practical information like standard fasteners, power transmission components, etc, and on the specification of these - making it useful for detail design, for instance. The section on the theoretical and mathematical underpinnings of engineering is relatively short, so it is of less use in the early stages of realising your latest brainchild. Like every engineer's reference book I have seen, it is also frustratingly inconsistent in the level of detail afforded to different topics.
Having said all that though, it's far better than many other similar books I've looked at, is based on UK/European standards and represents good value for money compared to trying to claw some of the information contained in it from the BSI at exorbitant prices. If you were to combine this with more a more theoretical reference book, you'd probably have the best "pocket" reference library you could manage with what's currently available.