Wow. I'm finding it hard to walk away from that book with any feelings other than 'impressed'. Also, 'scared as fuck'. I'm not sure if this is the best book of the series so far, because nothing can match the sheer skill of the plotting and writing in Hunger, but this was certainly the most extreme. Everything about the series - the darkness, the nightmare fuel, the mysteries, the complexity in the plotting - was amped up a notch. Grant's books have always been a pretty unique reading experience, but this is the book where that stands out the most, where it really comes to the forefront.
I do feel compelled to warn you that this book is scarier than before, and it features more 'adult' content. Up until now, a kid as young as ten could probably read the series with no problem, but that's not true anymore. The body horror was so intense that I think a younger kid would be really bothered, when they wouldn't be before. But if you are old enough to read the series, it makes the experience all the better. It's difficult not to be caught up in the intensity of everything, just because there's so much of it. Reading this book becomes a real experience, in a way that the previous books in the series aren't.
This shows up in the plotting, in a major way. Grant's pacing is, once again, wonderfully done, so that even when he's weaving four or five different plot threads together, they all feel connected and like they're moving along quickly. Adding to this feeling is the fact that the storyline is genuinely unpredictable, enormously increasing the suspense and the tension. I'm honestly amazed at Grant's ability to create a plot with such a large scope and connect it so effectively and tensely. I don't think I've ever seen anything like this before.
Of course, the characterization helps. As with the level of horror, the characterization is amped up a notch, but in a slightly different way. There's a certain bitterness to the characters that wasn't there before. Take Orc for example; I had always found him a bit shallow and uninteresting compared to the others. But this book shows just how depressing and fucked up his life really is, to the point that it's impossible not to feel sorry for him. Or Astrid; this book has her doubting her faith some, which she held onto for so long, and what she does at the end... well, you'll see. (Because you're going to read this series. Whoever you are.) Most of the character arcs that are pushed into the forefront are like this (Dekka, marry me and live on a houseboat), and it's just as impressive as the plotting.
The writing, up until now, has been my biggest complaint about the series. It's certainly not bad, it's just been a bit inconsistent. Some scenes are as smooth and effortless as a ballet teacher demonstrating choreography for first graders, others have turns of phrase so obviously awkward that I can't imagine how they survived a single read-though, let alone a long editing process. I'd say that Plague was in the middle in that regard. In the beginning, there was a bit of awkwardness, but it didn't affect anything too much, and by the end of the book, it was completely Gone. (I think I'm going to use that pun in every review of this series that I write...)
I wouldn't recommend starting the series with this book, but fans of the series won't be disappointed, and if you're not a fan, then you should definitely remedy that immediately. It's a very strong, well-written series with an almost universal appeal.