The 1979 edition (left) is the one I read and features my favourite cover. I got the 1981 edition (right) as that's the one most of my collection is in, though the cover isn't nearly as evocative for me.
The cover art for the hardback clearly represents the title, which is misleading in itself (there isn't actually a house that shrinks at all) and so, for the paperbacks, other aspects were played up - as seen here, in the 1983 edition.
In addition to being one of my favourites, this also has the distinction that each piece of artwork is completely different, focussing on a fresh set piece each time. The 1973 edition is on the left, the 1983 version on the right. I love the 1983 editions (did I already mention that?), so it gets my vote as the best.