There are a number of reference books available about Action Man. Below are listed all the ones that I know of.

Action Man
by Kevin King, Cairo Cafe Publications ISBN: 0953887006

Action Man
by Frances Baird, New Cavendish Books ISBN: 1872727360

Action Man, The Ultimate Collectors Guide Volume 1, 1966-69
by Alan Hall, Middleton Press ISBN: 1901706141

Action Man the Ultimate Collectors Guide Volume 2, 1970-77
by Alan Hall, Middleton Press ISBN: 190170629X

Action Man the Ultimate Collectors Guide Volume 3, 1978-84
by Alan Hall, Middleton Press

Action Man : On Land, Sea and in the Air
N.G. Taylor, New Cavendish Books