Science fiction heavyweight Jon Courtenay Grimwood introduces a new series with “The Fallen Blade,” the first installment of an urban fantasy set in 15th-century Venice. It has werewolves, and it has vampires, but if it sounds like “Twilight” in a time machine, think again. “The Fallen Blade” is bursting with political intrigue, epic naval battles, arranged marriages and assassins – and it doesn’t pull its punches. That last, if nothing else, is the mark of an author with worlds of experience at his disposal.

The cast consists of the characters one might expect – Lady Giuletta di Millioni, the runaway princess, and Atilo Il Mauros, the head of the Assassini, come to mind – but also characters who are intrinsically intriguing, such as the Mongolian-born mother of the half-wit Duke of Venice, the Duchess Alexa and the not-quite-human, semi-feral Tycho, who is discovered by a customs officer in a secret compartment of a Mamluk ship. The development of the characters is uneven (Giuletta, for one, seems incurably bratty, to the exclusion of other character traits), but even the less appealing characters demand the reader’s attention, as their stories are intricately woven together in a high-stakes Byzantine plot where one misstep might result in murder or war.

The story opens with a conspiracy: Duke Alonzo, Venice’s regent, hatches a plan to marry Giuletta to the king of Cyprus – with a di Millioni child already in her womb. She is to discreetly dispose of her husband and rule Cyprus in the name of her infant son, taking direction from Venice. If all goes according to plan, Venice will gain control of valuable trade routes in the Mediterranean and beyond – but Giuletta refuses to cooperate. She runs away from home and into the arms of Prince Leopold, the German ambassador, who has suspicious connections to the krieghund (werewolves) that have been terrorizing the city.

Their story dovetails seamlessly with that of Tycho and Atilo; Atilo’s famed and feared Assassini, in the beginning of the novel, is left in tatters after an encounter with the krieghund, during which he sacrifices the lives of the majority of his men to save the errant princess. Atilo needs an heir to his leadership of the Assassini, as all of the suitable candidates perished that fateful night, and Tycho, with his preternatural strength and speed, seems the perfect choice – Tycho, who has already encountered both Giuletta (in a church) and Atilo’s betrothed, the heiress Desdaio (in a prison cell), and has left an indelible impression on both.

The sheer number of stories happening at once, and the way Grimwood effortlessly juggles them, is eminently impressive. Never once does the reader doubt that he will resolve the disparate threads by the end of the book, though he could have stood to tighten the narrative by cutting some of the less-important viewpoint characters. Grimwood also uses his setting to great effect; it sometimes seems as though Venice itself is a character of its own. The city’s presence in every element of the story can, at times, seem overpowering, especially in the instances where setting and circumstance supersede characterization. Fortunately, as with many Byzantine novels, “The Fallen Blade” is a plot-driven book.

Grimwood’s latest work is a refreshing take on vampires and werewolves, where the supernatural takes a backseat to the story itself. “The Fallen Blade” is proof that such well-worn tropes are still viable – it merely requires a whole lot of talent.