It hardly needs to be said, but this is a beautiful book. A bit too big to easily find a comfortable way to read, but it more than makes up for it in quality. As someone who hasn't read these stories before - I had read a couple of the trade paperbacks before they started publishing the library volumes but since then I've been waiting for these instead - it's an amazing way to discover them for the first time.
The stories contained within certainly deserve the treatment they're getting with these volumes. The plots of the stories may not always be very complex, there seem to be few problems which cannot be solved by Hellboy punching something, but the stories still manage to fascinate. It's the mood that they evoke that draws me in again and again. They have the feel of old folk tales told for a modern audience, with dashes of Lovecraft.
Speaking of mood, the art is of course excellent and the main reason to get these oversized volumes. I didn't start out as a particular fan of Mignola's style but it has grown on me over time. This is a book full of shadows that somehow feel more alive than the most lifelike illustration.
In short, buy this book. It's hard to imagine getting better value for money, and story-wise there's nothing else out there quite like Hellboy.