Actually I'm now reading book 5 in the series - Wolves of Calla - but it seemed stupid writing a review for a book I'm only halfway through. So far it's been of the same standard as the rest of the series though, which is to say quite compelling but not a total page-turner. I have found myself thinking about where the plot is going next when I'm not reading them, which is always a good sign.
I bought the recent paperback release of the entire series. This includes a new author's introduction... the same one in each book, which is quite annoying. It's a series that is
really not suited to being read as anything except a series, so there's no point in repeating anything in one book that's in one of the ones before it. In fact, the start of book 5 even includes an author's note saying "If you're starting here, don't. Go back and read the previous four first".
Anyway, that niggle aside, I'm enjoying the books, and I'm certainly looking forward to finding out how it all works out. One of the principle characters isn't quite convincing at times, for me at least, but the rest are good, and the gunslinger is great - reminds me of the Saint of Killers from Preacher, and that's kind of how I see him in my mind's eye. The messed-up world they're (mostly) moving through is interesting, a sort of post-apocalypse wild-west, but with variations in how far things have broken down in different areas, and how the local residents have reacted to this, which keeps the world around them interesting for the reader.
I definitely wouldn't say I was a fan of Stephen King, mostly because I don't generally read or enjoy horror, but those of his stories I have read have been well written. This series is an opportunity to enjoy his writing ability in a different genre to the usual, and I'd recomend it to anyone who likes long epic stories and the whole post-apocalypse / degenerating civilisation thing.