One one of the many fascinating publishing details is that the UK edition was produced in two wraps versions as well as hardcover. As you might imagine the wraps variant is much rarer.
I can find no early Canadian editions of any interest so I'll discuss a few American in this post. I'll keep looking for an early Canadian edition.
The first paperback edition published in the US in the mass market era was the Armed Services Edition, one of 1322 titles published for American servicemen during WWII. In addition to its collectibility as part of this series this edition is almost unique in that reprints the first American edition. If you've read the book you'll be surprised how different this version is.
Armed Services Edition T-2
Armed Services Edition T-2 back