Having already got hold of "Grow your own cut flowers" by the same author, I agonised for a long time about whether to buy this as well. Although there is some repetition, there is also a lot of different material. There are more arrangements and techniques in this book than in the later "Grow your own...", more detail on floristry equipment, and more information about more plants, which are organised by time of year and colour in this book, rather than by bulb/perennial/annual/half hardy annual, etc.
Although the styling of some of the photos is perhaps a little dated, the arrangements still look fresh and modern, and could be adapted if you want something a little less prescriptive. My only real complaint is that you would need a very extensive garden to grow as much as she suggests you would require for the really impressive arrangements (highly invasive, pond-liner wrecking bulrushes? Really?), which would not be practical for most people.
However, this book is very much a step up in volume of flowers and scale of arrangements from "How to Grow Your Own Cut Flowers". If you are after larger scale and more variety, this is definitely a worthwhile buy.
(If you want to see more pages, search for it on google books - more are available than on "Search Inside" here.)