"Non-Jewish book collectors buy books according to their importance, and Jewish book collectors buy them according to their rarity," said the seller, a dealer who asked to remain unidentified.

The book, printed in Bologna in 1482, is also the first of any part of the Hebrew Bible to be printed with vowels and cantillation signs, and the first to appear with Targum Onkelos (an Aramaic translation) and medieval commentator Rashi's interpretations surrounding the text in what is now considered the traditional manner.

The copy had been presented to JTS by Judge Mayer Sulzberger, whose collection, donated to the institution in 1904, constituted the beginning of its library.

"JTS undervalued it and Christie's did a wonderful job of showing its true value," the seller said.

The identity of the buyer is not known, but it is not one of the known collectors of Jewish books, the seller said.