B. Netanyahu, one of the world's foremost medievalists, has made a lifelong project of studying the historical evolution of Marranism and seeking to ascertain the genesis of the Spanish Inquisition. In this seminal work, which opened an ongoing debate on the nature of conversion and belief in late medieval Spain, Netanyahu analyzes evidence on the Marranos contained in the Hebrew sources.

For this new edition, Netanyahu has revised and updated the book throughout and added a postscript in which he reconsiders the Marranos in light of the scholarship that has appeared since publication of the second edition in 1973.