Found this review on the book you recommended.
The book itself has some really spiteful and sarcastic overtones at times that plague this type of apologetics. Not only are his arguments weak on the scriptural side, but Keating manages to habitually use verses out of context as well as having a frequent habit of referencing the "early church writers" to prove his points with a suprising amount of historical irresponsibility. Now, in case some aren't aware, he makes mention of writers such as Origen and Justin Martyr to prove his points. Origen was a neo-platonist with gnostic tendancies who allegorized away the resurrection and denied hell as well as several other major Christian doctrines. Justin Martyr was a self proclaimed gnostic in his writings. The fact that he's allowed men with heretical beliefs into the mix should be quite disturbing to anyone--seeing as how you should always check the background qualifications of your references.
He also selectively uses writings from Ignatius and Irenaeus which conform to his arguments--but will omit the fact that both writers (more Irenaeus than Ignatius) also refute many of the dominant doctrines of Catholicism today, such as the authority of tradition (such as Irenaeus, Against Heresies, Book IV, c. XXXIII, sec. 8; and also Book I, c. X, sec. 2 written in 180 A.D.) or the fact that Irenaeus, in 180 AD, declares that Peter and Paul ordained Linus as bishop of Rome and then left the city: "The blessed apostles [Peter and Paul], then, having founded and built up the Church [in Rome], committed into the hands of Linus the office of the episcopate. Of this Linus, Paul makes mention in the Epistles to Timothy." (Adversus haereses, Book III, c. III, sec. 3). In case anyone misses the significance, Catholic tradition places Linus as the second "Pope" after Peter's martyrdom. Ignatius further reveals the Linus was Paul's disciple; Peter's disciple, Clement, came afterwards (Ignatius, Epistle to the Trallians, c. VII, first century AD). Irenaeus also refutes, in no uncertain terms, the notion that the bible cannot be interpreted by anyone but the Catholic Church and its clergy, "...therefore, the entire Scriptures, the prophets, and the Gospels, can be clearly, unambiguously, and harmoniously understood by all, although all do not believe them." (St. Irenaeus, Adversus haereses, Book I, c. XXVII, sec. 2). These are just a couple of small things, to say the least.
I could go on for a very long time, right on down the list of the "Ante-Nicene Fathers." The fact is, you can pretty much try and prove whatever you want as far as early church doctrines go if you look far enough into the early church writers. There's something there for everything. Heck, even the Jehovah's Witnesses can find stuff in there to prove they're "right." To be quite honest, you can prove or disprove aspects of the Catholic theology by using the same writers. St. Augustine (who's really good at debunking Mary doctrine, but has some really good quotes that can be used out of context to sound like he supports it--I've seen it done), St. Irenaeus, Tertullian (also good at debunking Mary doctrine--who, by the way, was a montanist--another heretical group). Depending on the chapters or passages you use and how out of context you use them, it's really hit and miss. The question is just who to pick and what to pick them for. They varied so wildly in their doctrines that you can't really trust any of them for the "definitive truth". I say all of this with a little bit of fecesiousness because it's rediculous to trust in these men for anything. Believe me, I've read them! They veered with every wind of doctrine, and agreed only to disagree.