Ken Hite is one of the most interesting and original thinkers working with the subject of Call of Cthulhu and Dubious Shards shows him at his esoteric best. He weaves together interesting bits of information that by sheer coincidence seem to confirm the most bizarre contentions of HPL while at the same time showing the prospective Keeper how to do the same thing. His knowledge spans enough different and seemingly mutually exclusive areas of knowledge to astound the reader with the bits of "corroborating" evidence he places throughout his topical wanderings, and yet he retains the joy of discovery as he does so. You fully expect him to exclaim at the end of one of his articles "And you can even use Zeppelins!"
Dubious Shards is another collection of his articles, this time focusing on some of the more salient features of Call of Cthulhu, including Irem of the Many Pillars, Dunwich, "Yog-Sothothery" and its use by the Keeper to evoke atmosphere and develop scenarios and even campaigns, an article on HPL himself, and so on. While his guidance scarcely falls into a "step-by-step" guide, he does evoke the spirit of HPL and provides some data that can be used by the dedicated Keeper to begin researching his own connections. Perhaps his most important piece of advice, however, is to "become paranoid" as you read through history in order to permit yourself to make those same leaps of connections that the truly insane can and do, and which are fully in keeping with the nature of the creatures (and their nefarious plots!) that Call of Cthulhu brings to the harsh light of day. The articles are interesting, and as noted, permit the reader to look up other bits of information and formulate ties between them, all the while keeping the idea of the mythos clearly in front of the reader.
In addition, this particular book includes a complete, ready to play Delta Green scenario. While I generally stick to the 1920s for my CoC campaign, I'm told that Delta Green is far and away the best modern era construct revolving around the mythos, and from what I saw in the scenario, it's a very good one with plenty of suitable places to hang additional plot hooks and adventures from.
All in all, I rated it a four -- simply because I'm NOT a fan of anything much outside the "classic" era of CoC and thus felt part of the book was "wasted;" however if you like modern era CoC, I'm betting you'll rate this book a "five+!"