Duffie, Peter: Duet ©1984 Peter Duffie Softcover, comb-bound, 8.5x11", 13 pages

Image courtesy eBay seller USToy_Magic

Comments:Also included in a compilation book Subtle Miracles (2004) along with Trio, Quartet, Solo, and Double Indemnity.
Uses blank cards and a gimmicked card you can make yourself.

Contents (numbers are not page numbers):

1 Point Blank Assembly: four Kings changes places one at a time with four blank cards, and more!
2 Impulse: starts as a transposition effect between a selection and a blank card, but ends with a surprise