I had the same experience. I thought I had made sure that this was the trilogy before I ordered. I also checked the Search Inside facility, which sent me to the paperback edition, so it was no help and indeed was misleading. Your review had not appeared when I ordered the book, otherwise I might have thought again; but now it is here and it looks so pretty that I decided not to send it back. I don't like the cover of the paperback trilogy edition, so I shall just wait until it is redesigned before replacing my ancient and disintegrating copy. Amazon can be very slapdash about product descriptions, especially where there are multiple editions, and they are no better with DVDs and CDs than they are with books. It is their one failing, and I hope they will address it, as it mars their otherwise excellent standard of service.
Edited to add: I am also annoyed with Virago for failing to include the two subsequent volumes in this very attractive edition. It seems needlessly mean just to use the first volume; 'Wartime' is in some ways the most interesting of the three.