On opening this for the first time I was initially disappointed. Basically it's just page after page of photographs of plants, most of which have been picked/uprooted and laid out for the camera. I wasn't sure how I'd go about identifying anything short of leafing through everything page by page until something looked "right".
As it turned out, it was surprisingly easy to use. I saw a couple of things I didn't recognise, took a picture and when I got home checked the book. The pictures are arranged by time of year - so, being early (April) I focussed on the April/May section and located likely candidates within a few moments. It also has references to other plants that look similar so you can check those to make sure you've got the right one. A real pleasure to use.
A couple of things to note though. First, some of the pictures are quite dark or the plant is small so detail is lacking. I think it would be tricky to use this for more "advanced" identification. Second, it's fairly big - about A4 size - so you can't really just slip it in your pocket when you go out. Finally, the text detail on the plant is very basic - just a few sentences.
Overall I'm really glad I got this though, it's quick and easy to use and doesn't feel academic or over-complicated. It's good for basic identification, but I think if something more detailed or comprehensive is needed you might want to consider another book, maybe "The Wild Flower Key" by Francis Rose.