The focus is exclusively of world maps. The book has (surprisingly) a very interesting text to accompany the pictures. Unfortunately, the picture resolution is not great, but all the pictures are in colour. You can actually find better resolution pictures on wikipedia, but buy the book for the insightful text.
An alternative is The Map Book. It has the same theme and more than double the number of maps than the current book. Also better resolution images, but much less insightful text. So this book as the feel of a coffee table book for the intellectual man.
If you love maps, buy both. It is interesting to note the differences: This alternative book shows a Medieval huge map that was bombed by the Brits during the war. The book under review does not even mention this masterpiece but instead notes that continental Europe was not so interested in world maps at the time. Okay, I'll stop making esoteric comments.
I can really recommend the book. Four stars.