I interpreted it as having three main themes:
I. Prof. Feser really doesn't like the New Atheists. Really, really, really doesn't like them. Likes them so little it makes Osama bin Laden's view of America look like mild distaste, or Fred Phelps' views on homosexuality look like reasoned neutrality.
II. The conflict typified by New Atheism is not a conflict between science and religion, but a philosophical conflict between an Aristotelian philosophy that leads inexorably to religion and a mechanistic philosophy that leads inexorably to atheism, with science sitting quietly on the sidelines. Things that seem stupid, arbitrary, or hypocritical about religion are stupid only when it is viewed in the context of mechanistic philosophy, but make perfect sense within its own system. Faith is not involved, and there can be both reasonable religious people and reasonable atheists (though Feser would no doubt put the second "reasonable" in quotation marks and follow it with a "DIE DIE DIE I HATE YOU SO MUCH")
III. The Aristotelian philosophy that leads inexorably to religion is correct, the mechanistic philosophy that leads inexorably to atheism is false, and the current dominance of the latter is due to a historical mistake.
II is going to take a lot of time to unpack; III is going to take forever although I intend to try. I have only a short time tonight, so I want to concentrate on I, the mountains of abuse that Prof. Feser heaps upon atheism for several chapters before the book begins and at very regular intervals throughout. In particular, I want to say exactly what I think about this style of unabashedly and unnecessarily nasty polemic.
I like it.
I hope I won't be offending anyone here too much when I say scholastic philosophy is super boring. You know how philosophers start talking about universalizability and the sense-reference distinction and stuff and normal people just tune out because who cares? Well, when scholastic philosophers start talking, regular philosophers tune out. My professors at college explicitly treated scholastic philosophy more shallowly than most other schools because it was unpleasant to think about for too long. The archetypal boring useless question - how many angels can dance on the head of a pin - originated as a criticism of scholastic philosophy, and although there is no proof that scholastics actually discussed this they definitely explored very similar areas (Aquinas discusses whether multiple angels can occupy the same space; he concludes they cannot).
But Culture Wars are super interesting, in a horrible sort of way. I'm not saying that they should be, or that they don't appeal to our worst in-group / out-group / take-some-people-who-think-slightly-diff
So when Feser says that he thinks gay sex is objectively horrible and that anyone who thinks otherwise is hopelessly confused, this creates just enough of a dopamine surge to make it possible to read another three pages about Aristotle, just to figure out how he got so wrong. When he says so a hundred times, you end up reading a three hundred page book about Aristotle without even trying, whereas otherwise it's not always easy to get through a Wikipedia article on this stuff.
Looking back, I realize how much of what I have learned in life I learned for terrible reasons. When I was young, I read some books about the Lost Continent of Atlantis, and wanted to see if it really existed. After devouring a bunch of ancient history and mythology it turned out it probably didn't, but this was a much quicker way to learn lots of ancient history and mythology than picking up The Oxford Compendium Of Extremely Dry Scholarly Papers About Near Eastern Pottery and hoping for the best. Reading Velikovsky didn't hurt either. And how many people would know anything about evolution nowadays if you didn't have to read TalkOrigins to debate creationists?
I guess what I'm saying is that it's really hard for me to really learn unless something is pushing me. When you're young and you have a lot of unanswered questions you have a lot of push. When you grow older and start accreting answers to those questions, it's harder and that's bad, even though some of your answers might be wrong or meaningless.
Sometimes humor and good writing work. Douglas Hofstadter, by means of awesomeness, got me to read a book about Godel's Incompleteness Theorem, which is prima facie pretty unlikely. Sometimes dangling the promise of vast new hidden knowledge does it - I can read all day about occult orders and conspiracy theories even though I know they're wrong.
And sometimes, you've just got to say something implausible and enraging, then tell me that I don't know enough to respond intelligently until I read three hundred pages about scholastic philosophy, and keep taunting me a few times each chapter until I finish.
There are good ways and there are bad ways to do this. In particular, Feser specifically acknowledges many atheists can individually be intelligent and morally decent people. He promises that he will explain each of his insults and why they are correct, then goes on to actually do so. He doesn't take too many cheap shots (except when talking about the "Four Horsemen", for whom he has a particular loathing). And something about his criticism stands out as an invitation to a fair fight rather than a bullying attempt (which I don't get with, say, criticism from some of the worse forms of atheism or feminism or political extremism). It may be that it's criticism without Bulverism, an insistence that the other side is legitimately wrong about a legitimate question which is legitimately worthy of debate; in fact, his criticism is often that they are not debating the topic with the gravity it deserves. Or maybe - in fact, most likely - it's that he's criticizing from a position of weakness and so lacks the threat of social stigma possessed by more popular groups. Oh no, the Catholics don't like me! What are they going to do? Write an angry encyclical?
In any case, good work. I just spent three hundred pages reading about Aristotle and scholasticism, which is not something I expected to do. I can only hope that someone will one day write a book called Updateless Decision Theory and the Global Warming Hoax.
[NOTE: Other times when people are angry and insulting, I get extremely upset and never talk to them or read anything they've written ever again. This is probably more common when it's in a personal discussion as opposed to a mass-market book. In any case, I wouldn't recommend trying it.]