Rather than a book maybe a subscription to a monthly magazine such as Gardeners World....with helpful advice throughout the year might be useful for your friend.
There seems to be a consensus for the Alan Titchmarsh book. You can buy the hardcover version new from Amazon, either for £396.19 or, if you want to show your friend how much £££££ you love them, for the hefty sum of £1,999.
Gardener's World subscription is a great idea - I have one from my daughter. Each Christmas she taps out a little letter telling me that she has renewed the subscription and just so I have a package to open too, she buys me some packets of seeds. Gardeners World covers all aspects of gardening from encouraging wildlife, growing fruit & veg, starting a garden from scratch, container growing, pruning, seed sowing etc. your friend wouldn't be disappointed with this magazine.
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Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
Other online booksellers are available
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
In the sticks near Peterborough