Jimmy Cornell's credentials to write this are impeccable, he is the much-travelled founder of the ARC (Atlantic Rally for Cruisers) that is now in other hands. He has also published a number of pretty good local area cruising guides. I keep bumping into people who have met him without having had the pleasure of meeting him.
The book covers a lot of territory - so it is inevitable that _some_ routes are not included. However it is my experience that even some pretty tricky ones are handled in chartlet or text. This can call for some chapter-shuffling when (say) moving from the Med to the Red Sea and on to the Indian Ocean, but mostly the chapters are in a logical sequence that makes this easy enough.
Most trips will call for considerably more information than this or any other book can contain. You will still need charts, Pilot books and maybe a pilot atlas for local details. This book is (as intended) ideal for passage planning, and deciding when (eg) it is best to arrive at Suez to make a Red Sea passage. This in turn can control the departure date from the western Med, and so on. Copious waypoints are provided throughout.
As with any waypoints, it's worth checking/plotting every single one on the chart before using it. Not that I have found errors in this book, but oh dear, the books and almanacs that are flawed! 300NM (yes really) errors are obvious. It's the small ones that put you on the reef.
Good information on seasonal weather patterns is included, and there is usually a suggestion as to the best season for a given leg or voyage.
Weakest part is the idiosyncratic index which can cause delays finding what/where you want, otherwise it would (imho) warrant five stars. But it's worth persevering with a search since there is a mine of information in there.
Safe landfalls, Ben and Olly.