Irritatingly, my (undated) copy omits the prefaces. However, one of the online versions appears at least to have the 1834 preface, but I'd be interested in reading the 1850 one some time.

When I finally write the sf/classics book, I am going to have something about elements of the fantastic (usually accurate prophecy) in otherwise non-fantastic works like The Last Days of Pompeii) and I, Claudius.

Right, off to watch Who.