He listened to the human intently, although his demeanor was casual.
“Yes,” said the human.
From the sound of the E, he discerned that the human was probably from either near Boston or near Sydney. A human from Scotland might pronounce the E the same way, but only if he were impatient. And the human's phoneme pacing, as well as the slow pulsing of blood in his face, showed that he wasn't impatient. A bit curious, perhaps. Interested. But not impatient.
“Why did you buy it?” he asked the human, in a voice meticulously calibrated by a linear model on tens of millions of hours of wiretapped telephone conversations, whose only remarkable feature was its featurelessness.
“Well, I'd heard of the title, but I had never seen a copy in person. So when it came up for auction, I put in a low bid, and it turned out to be the only one.” The human's eyes flicked down a couple of times, punctuating his speech.
In the fillip the human gave to the word “auction”, he glimpsed childhood memories of weekends listening to the gavel, clearly from the contraband auctions the Coast Guard held at Back Bay every second Friday, and his secret joy in acquisition, along with faint hints of an adolescence spent masturbating in surplus military fatigues. In the accent he heard the traces of the human's parents' accent — Portagee, as they'd call it themselves. And in the tiny hesitations he heard the wounds of a childhood at the mercy of a sadistic parent, the human's father, probably. The timeframe of the Portuguese accent influence would be the 1950s or 1960s, and the human had grown up in poverty, with guilt attached to his love of books, so probably his parents were not highly educated.
Ah, it came into focus: the father had served briefly in PIDE, Salazar's secret police, and then fled Portugal to escape the horrors of what he had done in Tarrafal; but the monster awoken in the man fed on his son's soul even today. Every word the human spoke gave subtle evidence of it, to those who knew how to listen to human speech.
He knew how to listen.
The human was lying when he said he'd never seen a copy in person, he could tell, but the lie was motivated only by a desire to keep the conversation interesting. He hadn't been interested in the other copy he'd seen, but for a boring reason, and he knew that boring clients was no way to sell rare books.
Where the light glinted off the cover of the book, he recognized the fingerprints of half a dozen long-dead rare book dealers, but although he noted their identities for eternity, the book and its history did not really interest him. He was hunting down a conspiracy of rogue archivists who frequented illicit book dealers like this one, and who particularly might be interested in nineteenth-century chemistry books. But their fingerprints were not among the prints on the cover, and the human's speech and motions gave no suggestion they had been here.
No matter. Soon he would find them. They had no chance. Today he would set a bait here, tomorrow elsewhere; sooner or later they would buy a book from someone he knew, or carelessly leave a fingerprint on the subway, or talk to one of their family members, who were all under surveillance by casual acquaintances who seemed human.
“I have the next one in the series,” he said to the human in his voice, a voice so average that to another like him it would stand out like a siren. “Would you be interested?”
In the human's face he saw a lifetime of hopes, dreams, fears, obsessions, and disappointments flicker by in a fraction of a second, and then heard them richly modulated onto the human's casual voice: “Could be.”