12574 Robert Chassell: Programming in Emacs Lisp. 1995. 1-882114-41-8. $20.
Perhaps out of print. But on the web.

Glickstein: Writing GNU Emacs extensions - make your own editor through
Lisp and customizable features.
O'Reilly 1997, 250p. 1-56592-261-1. DM 59.

Bil Lewis/Dan La Liberte/Richard Stallman: GNU Emacs Lisp reference
manual. Internet 1998, 820p.

William McEnaney: Programming techniques in Emacs.
Prima 2000, 400p. DM 87.