in conn iggulden book "Emperor - The Gates of Rome" they refere to the book gladiator, who is the novelist .

Question

Emperor is a series of four books relating to Julia Ceaser, Gladiator is supposed to have been written prior to these books, we can not find the author or the book.

Answer 1

from Amazon could this be it:
The Gladiator by Sean O'Kane (Paperback - Sep 2003)

Answer 2

The Gladiator: The Secret History of Rome's Warrior Slaves by Alan Baker ISBN0091886546, this might be the book you mean.

Or perhaps Gladiators: Spectacle and Entertainment in Ancient Rome by Rupert Matthews.