It is some measure of Dunnett's prodigious energy that the sixth volume in her ongoing series about the adventures of Nicholas de Fleury, a charismatic Renaissance-era rogue/merchant prince (The Unicorn Hunt, 1994, etc.) begins with a seven-page list of series characters. And it's some indication of her considerable narrative talents that the complex schemes and obscure quests of her protagonist remain generally gripping through the course of a 600-page novel. Like earlier entrants in the series, this latest offers a dazzling portrait of Europe's courts and countinghouses in the 15th century. Set during the turbulent years 1471-73, the novel follows Nicholas as he extends the influence of his trading house, the Banco di Niccolâ€¢, deftly plays both sides in the war between King Louis of France and the Duke of Burgundy, and attempts to survive the efforts of the Vataddino, a shadowy rival trading empire, to destroy him. There's also a vividly rendered expedition to Iceland that includes a remarkable battle at sea and concludes with Nicholas's supposed death. Of course, he survives, once again confounding his enemies. At the heart of the story, though, is his battle of wits and wills with his estranged wife Gelis, the only person who can match his inspired schemes. Blaming him for the death of her sister, she has set out to humble him, even going so far as to work for the Vataddino. To best her, to avenge old wrongs, and out of sheer Machiavellian bravado, Nicholas sets in motion a plot that could destroy the Scottish throne, damage the Vataddino, and (he thinks) win Gelis back. But for once, even the King of Secrets (as he's called) cannot control the outcome. Dunnett's pace is robust, her grasp of the Renaissance mind subtle and convincing. But the self-absorbed Nicholas is becoming, after 3,000-plus pages of text, a bit wearing. That isn't enough, though, to much tarnish the best modern series of historical fiction.