It's not as though that is anything new with Amazon - consider the following, from the same order:
What Amazon have to say about Estimated Delivery Dates:
Estimated Delivery Dates
We do our best to accurately estimate when items will be dispatched from our fulfilment centres and from other sellers on Amazon.co.uk. Estimated dispatch dates are based on several factors, including your destination address, how quickly we can obtain and assemble items for dispatch and whether you have requested that we group your items into as few deliveries as possible.
Our estimated dispatch dates are always a range of dates. It is entirely possible for an item that has not been dispatched by the beginning of the date range to still arrive within our delivery estimate.
We calculate delivery estimates by taking our estimated delivery dates and adding the time it takes a package to travel from our fulfilment centre to your destination address.
Sometimes we'll update our delivery estimates based on the most recent information we have, so please remember to check your estimated delivery date in Your Account.
It's not that I don't understand that sometimes it is difficult for Amazon to get hold of books (though I wonder how it is that a book that Amazon USA can deliver within 24 hours is so hard to get in the UK, that Amazon UK has twice warned me of delays in it), but when they estimate a delivery date that is in the past when the item has not yet shipped, does not inspire confidence.