A fine book.  I can't find an online copy of the complete text, but this site has the essential material for unlearning the lies.  Roth, the Jew historian, attempted to smear Walsh and was trounced, naturally.

Isabella of Spain by William Thomas Walsh (.pdf)

This book has a large amount of information about Jews in medieval Spain. It
repudiates the works of Lea and Loeb, who seem to have established much about
what people today think they know about Spanish Jews. Originally published in
1930/1 (New York: Robert M. McBride Co., xix + 515 pp.; London: Sheed &
Ward, 644 pp.). Later editions (e.g., New York: Tudor Publishing Co., 2nd ed.,
1938) re-wrote some passages to be a touch milder, and deleted some nasty terms like "Ritual Murder" and "Jєωιѕн Conspiracy" from the titles, but the raw info remained in all its pungency. All scans from the 1st edition text.

Commentary and Reply: Dr. Cecil Roth and Walsh regarding this book.
See the the sparks fly! Walsh thoroughly trounces him, too!