Peter Toon is an Anglican affiliate cleric who is the author of this book. I have to say as an apologetic work it serves its purpose well, although I wouldn't say it tops alongside the works of Fr. Thomas Joseph White O.P., Fr. Giles O.P., and some others when it comes to both Christological and Trinitarian teaching. Toon's book is mostly a historical overview but he does not at all hold back from counting the errors of heretics, explaining them, and then rebuking them. There is an entire chapter dedicated to the Fathers monarchy, the Sons divinity and the filioque which is that procession from the Father through the Son or Father and Son, however you may want to describe it.
VERY REMARKABLY, as an Anglican, he showed high reverence to the 2nd Council of Nicea and Icon Dulia. Even having written some words of lost and sadness that some of his Protestant brothers could not seem to enjoy the orthodoxy of this council against the pseudo-council of Hieria.
I did however leave a four-star rating due to some issues I've had with his writing somewhere in-between the book. He is staunch on the claim in believing Pope Honorius was a formal heretic for one, a belief that his successor, Pope St. Leo II did not condemn him for with Pope John VI and St. Maximos the Confessor at his defense. The very sad belief that also tainted Sergius of Constantinople, who may have not been a monothelite.
Other than such claims like these, I find most of the book to be very good and enjoyable. One of the few Anglicans I had pleasure reading.