The Fallen Blade by Jon Courtenay Grimwood

The setting is Venice, 1407. La Serenissima is effectively ruled by the Council of Ten, responsible for the security of the republic. Titular head is Duke Marco, descendant of Marco Polo, but the real ruler is his uncle Duke Alonzo, Regent because Marco is a halfwit. To maintain its role as one of the most powerful of the Italian city-states, alliances are necessary, and Duke Alonzo has the power to dispose - in all senses of the word - of family members to meet political expediency; to this end he has decided that his niece, 15-year-old Giulietta, will be married to the King of Cyprus. Desperate to evade her role as a political pawn, deserted, she thinks, by the aunt she has trusted, Giulietta flees, but is caught and returned by Atilo (until recently, Admiral of the Venetian Fleet, and still secret head of the Assassini), after witnessing a terrifying street battle. The night before she is due to sail to Cyprus, Giulietta, filled with horror by the knowledge that she is to bear a son to the King and then murder him, escapes again, this time to the Basilica San Marco, where she intends to kill herself. Instead, she meets a mysterious, silver-haired boy. We've already seen his arrival in Venice, incarcerated in the hold of a Mamluk ship, bereft of memory, nameless, and shackled with silver chains.

There are books that draw you in from the very beginning, and this is one of them. There is a flow to the story that keeps you turning the pages long after you should have turned off the light and settled down to sleep. The cords of the story are expertly woven, each character's thread  - and there are more to follow than Giulietta's and silver-haired Tycho's - reappearing just when the need to discover what has happened to them becomes too insistent to ignore, so that you feel just one more chapter can't be resisted. If it lacks quite the savage brilliance of some of Jon Courtenay Grimwood's earlier books, The Fallen Blade is nonetheless very hard to put down, and as Act One of The Assassini, it promises great things. As usual the characterisation is excellent - he's particularly good at young women - and he has a gift for keeping you absorbed in the dangerous characters as well as the sympathetic ones: they might be brutal, ambitious and ruthless, often charming, sometimes appalling, but their motivation is always understandable and their single-mindedness can even at times seem laudable. In other words, they are complex, multi-faceted individuals, and your interest is held because they seem real and unpredictable.

JCG mostly eschews the long descriptions that some authors use for scene setting - where they are used they are sparing and always advance the action, or your understanding of it, but such description as is included builds a strong sense of place - at times, you can almost smell Venice. There's grandeur here, and squalor, and a cast of warring factions whose allegiances could never be relied upon, liable to turn at the slightest spark. It's an alternate history so close to reality that it's utterly plausible, and the reader slips between the real past and the imagined one as easily as Tycho slips between his real city and the invisible one which shelters him when he is first cast adrift in Venice. Vampires and krieghund seem native to this dark and watery city, where assassins lurk not only on every calle but also in the palazzi of the rulers, and poisoning is the quickest way to get rid of a rival. At the end of the book much about Tycho's nature, too, remains to be revealed - bring on Act Two.