After a quiet period where they've been felt more by their legacy than as an active threat, the series' big bad, the reptilian Annunaki are back with a vengeance. Quite literally in the case of living rock giant Ullikummis, emerging like Superman from a shoal of meteorites after millenia of exile.

This book feels a lot like the opening chapter in a much bigger story and perhaps suffers a little from the amount of exposition involved in setting up a new saga. The main plot is consequentially quite slight, essentially the first skirmish between our heroes and a new villain.

It's strongest parts are those that delve into the givens of the Outlanders series, raising questions about the true purpose of the villes, why the  Annunaki only inhabited North America and a unseen consequence of Lakesh's rejuvenation. I suspect there are other threads, such as the romance between two secondary characters and numerology that will become more significant in later books. In television terms I would describe this as an arc episode.

This is the first book I've read with a substantial Annunaki presence and the flashbacks to the height of their power were intriguing, the best being the cruel and chilly court of Tesub with its dying dancers. The action highlight is the opening battle with zombies in a voodoo temple, very dramatic and well written. There's also a touch more humour than usual, especially Bridget's teaming up with a new pair of operatives. In all its good to see the overall development of the Outlanders saga picking up again.

Oblivion Stone is a very interesting book, one that introduces a new primary antagonist while at the same time calling backwards to the long history of the series. It is also the fruition of many plot seeds that have been sown in the past half-dozen books. Where previous stories like Death Cry, Janus Trap and Infinity Breach gave us glimpses into the other-dimensional aspects of reality, and Shadow Box teased with some glimpses of the Igigi at the height of Annunaki power, Oblivion Stone pulls it all together with the introduction of Ullikummis.

The story opens with a solid action sequence in the Louisiana Bayou, complete with ancient alien artifacts and shambling zombies. At the peak of the action the team loses their link to Cerberus, which has been tossed into disarray with the sudden complete failure of both orbiting satellites and all of their attendant communications abilities. As the Cerberus rebels struggle to identify the cause of their complete communications blackout, up in Saskatchewan falls to earth the Son of Enlil, Ullikummis.

With Ullikummis' arrival also comes a significant amount of back story that explains the origin of the obsidian blade Godkiller that featured so prominently in the previous novel Infinity Breach. In fact, a very large portion of this book is spent in flashbacks to Ullikummis' childhood 4,500 years earlier during the peak of Annunaki power.

Interestingly, I found Ullikummis to be a surprisingly sympathetic character. Where Enlil and the other Annunaki come across as pure egocentric evil, with Ullikummis we are given insight into the childhood that forged him into his identity as a Stone God and although that does not make him any less dangerous to humankind it certainly adds some interesting color to his personality.

Because this book acts primarily as a setup for a significant new storyline, it becomes fairly light on action during the middle of the book. It is not boring by any means, but for the majority of the book Kane, Grant and Brigid are split up and teamed with other "second string" characters. This provides for some nice character development, but it is only in the final chapters of the book where we get to see the Three Heads of Cerberus (plus Domi) fighting side-by-side.

On the whole it was a very enjoyable book, particularly in the way plants the seeds for multiple upcoming plot threads. I am looking forward to seeing where this is going.