This seems to be the 'Oz Clarke version' of the more well known 'Hugh Johnson's pocket wine book'. So is it any good? Yes.
It is the same size as it's competitor (pocket) and is primarily a wine buying guide combined with very-mini-encyclopaedia, it also has useful mini-sections on food, producers, buying tips etc. It's easy to read and user friendly. Oz puts in plain English what you need to know without ever assuming that you know your St-Julien from your St-Joseph, and without ever being condescending either.
Unlike Johnson, Oz's book is A-Z which makes it a bit more fool-proof (Johnson is organised by country, then A-Z). If you are a hardcore wine buyer, and would never dream of confusing St-Julien with St-Joseph, then Johnson is probably a bit more your thing, but for the rest of us Oz Clarke's approach is light, fun, helpful and instructive.
(The only down side of this great little book was that some wines were hard to find, being listed in subsections rather than under their own name. Otherwise, 5 stars !)