I re-read Hawking's 'The Universe in a Nutshell' whilst on holiday and am now fairly clear on imaginary time. CH's explanation helped.
I must say, however, that this latest book does nothing to improve Hawking's reputation. Apart from the fact that it's an American publication with all the usual, irritating, transatlantic illiteracies such as 'color' and 'fit' instead of 'fitted', the diagrams are very poor. In an attempt to increase the book's appeal to the non-scientist, the illustrations are of an ersatz 19th Century Science Fiction style, thus making them difficult to understand. This is not helped by the fact that some text figures are not properly labelled or don't have a scale for the graphs. The text is, however, pretty lucid.
In the introduction, Hawking says that he intended to produce a sequel to A Brief History of Time which is more readable and easier for the layman to comprehend. If that be so, his publisher has let him down. ABHOT is, I think, a much more informative book and an enjoyable read.
By contrast, I'm just coming to the end of John Gribbin's 'In Pursuit of the Big Bang'. It's better written, contains more information, uses mathematical expressions where they are helpful, has excellent text figures and, since it's a Penguin paperback, costs less that Hawking's book.
It's sad to see a prominent mathematician's work being dumbed down and I can't avoid the conclusion that Hawking's uniqueness has turned him into a 'brand' which is being shamelessly exploited.
:-band