I think that's simply due to the fact that "The Snowman" was the first or second book published in the U.S. Tigus said in his comments on my "Snowman" review (as part of one of my Halloween Bingo updates) that people started to wonder about the order of the books when the American publisher eventually started publishing all the earlier books, too -- particularly "The Redeemer", which is the immediate prequel of "The Snowman". Yet, many folks still seem to consider "The Snowman" the first one -- at least symbolically if you will -- simply because it was the first one to be published in English.

I was asking because, obviously, Harry is still around in "The Snowman", and struggling to stay sober, so I'd been wondering if he'd had a relapse and was now going to be booted once and for all, or if this was possibly the book that brought about his decision to face up to his alcoholism.

That makes sense, but I was unaware of this before. But I've heard about other series where they have started translating the earlier works of a series, and it is always confusing.

Yes, the same thing happened with Mankell's Wallander mysteries, too, I think.