The book is finally on sale. You can buy it here for £12.99 or, grab a used copy for £1,179.86 – I kid you not. I would be hard put to deny that the latter price reflects its true worth, but I suspect that UKPaperbackshop is not going to sell many books (and they charge postage and packing).
UPDATEHaving decided the book was for sale (and having delivered most-pre-orders today, Saturday), Amazon has now decided that the book has not yet been released has thus reverted to "pre-orders". What has probably happened is that Amazon has run out of stock and, since the book is not officially launched until 8 March, the computer has reverted to "not yet released". In the meantime, the overall ranking went briefly to 854, and the book holds its No. 1 ranking in Battle of Britain books.