The television series of the same name went out in the 1980s, and this "book of the series" was published soon after. Since then, a lot more books on traditional gardeneing and heritage vegetables have been printed, so why buy this one?
The BBC documentary was, in fact, the beginning of the resurgence of interest in walled gardens, "heritage" varieties and vegetable-growing in general. It was an enjoyable and informative study of the world of the Victorian head-gardener, and in these pages anyone who likes social history will find much to interest them. If this was all, the book would be worth having. However it is also a complete guide to the world of traditional techniques and varieties, often illustrated with the original engravings. If you are lucky enough to have a large area to play with, everything you need to create your own kitchen garden is here; if you have a more normal veg patch or allotment, you'll find plenty of inspiration too.
In recounting the research and sourcing for the programme, Jennifer Davies tells us a huge amount about how to restore an old garden, how to grow unusual and forgotten vegetables and how to properly graft, train and care for fruit trees. When the book was first published, many of the plants, seeds, and tools mentioned were unobtainable. Such has been the interest since that heritage vegetables are in every garden centre, tools manufacturers have restyled their ranges to look "traditional" and catalogues offering things like lantern cloches and rhubarb forcers (albeit at a price) fall out of every weekend broadsheet. This means that anyone wanting to create a traditional garden for themselves is now well catered-for.
If you're interested in this field, seriously consider
The Gardener's Assistant voumes 1 to 6; it won't be particularly cheap, but it is the best original period text and still very useful today. If you want to do it Victorian style it will have everything you could ask for; I suspect it was used in the setting up of "The Victorian Kitchen Garden" for television.