Whatever your view of the truth behind the various claims in this book (and if your of a ration frame of mind you'll probably be more than a little sceptical) you can't deny the importance of this book in the developement of what Professor Ronald Hutton has called 'The Second Romantic Age'.
In the sixties the Beatles went to India for a spiritual experience. What this book showed is that sacred landscrapes can be found much nearer home. Michell took something old, Alfred Watkins's The Old Straight Track, something true, archaeological evidence for astronomical alignments at Stonehenge, and something esoteric, Chinese 'Dragon Lines, and welded them together to produce a something new and original.
Scientifically speaking it might not stand up to close examination, but the result of this book, and its successors, is to Re-enchant the British landscape and make people look for the numinous in England's Green and Pleasant Land.