Rated by buyers 
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This book fails both as science fiction and as military strategy. It reminds me of the worst academic military strategy books, full of charts and manufactured statistics, unleavened by practical military experience. The few valuable insights could have fit on one page.
Rated by buyers 
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... now they just need some guys who understand the "scientific" bits well enough not to screw them up, a guy who can "write", and, oh --- an "editor" would be nice as well.
So it reads like a very first draft of a term paper by an enthusiastic but academically mediocre freshman --- what else is wrong?
Lots.
Since I'm a scientist, I'm going to focus on the science part of this book (the very first 60 pages --- for the record, though, I have read the whole thing). I have no strong opinion on the factual content that follows p60 (the writing is uniformly terrible throughout the book), but the science part is drivel. Here are some of the major problems with p1-60:
(1) (Not really science but something needs to be said) The dedication (p5) states quite baldly that "we must prepare for alien invasion because of September 11th" (I'm paraphrasing). Is that number 439 or 440 on the conservative wishlist of actions that must be taken "because of September 11th"? Help me out here --- I'm losing count.
(2) On p17, the following "argument" is given (again, I'm paraphrasing): "There is at least one intelligent civilization in our galaxy. Therefore, there ought to be at least one intelligent civilization in every galaxy. Since there are billions of galaxies, there ought to be billions of intelligent civilizations"! By the same logic, since there is at least one person in the square foot of the earth's surface that I'm standing on, and since the earth's surface area is about 5 million billion square feet, there should be at least 5 million billion people on this planet. Get it? Got it? Good.
(3) The treatment of Drake's Equation is nonsensical. DE is a fun toy for thinking about ETs, but since we have ABSOLUTELY NO INFORMATION about how big or small the last couple of terms are, DE allows us to infer NOTHING about the existence of ETs. And certainly not to write bold-faced drivel like (p26): "So, more than two hundred thousand traveling civilizations should be in range of Earth!"
(4) (Not really science but something needs to be said) If you're not American and you buy this book, be prepared for a lot of jingoistic flag-waving.
(5) (Not really science but something needs to be said) If you're a Democrat and you buy this book, be prepared for the obligatory bouts of (i) Reagan Worship, and, (ii) Clinton Bashing.
(6) Another reviewer already tackled the authors' (willful?) misinterpretation of the Fermi Paradox. 'nuff said.
(7) There's a breathtakingly stupid endeavor to use the Central Limit Theorem (think back to your Intro Stats course) to ... well ... Actually, I can't bring myself to say it, so I'll just quote from p57: "From the logic of the central limit theorem we can extrapolate that the types of creatures and their motivations that could exist in our universe should follow a Gaussian distribution" (which, for the uninitiated, means a Bell-curve). No. Actually you can't. This is wishful thinking that belongs in an SF novel, not in a serious nonfiction book. Oh, and, read the list of "normally distributed phenomena" on p56 with skepticism. Contrary to what the authors claim, some of those phenomena are not normally distributed.
Sigh. Let me finish by hoping that some day the authors hire someone with a proper scientific background to completely rewrite the very first chapter (I'm not volunteering). It'd be nice to see a serious book on the subject of alien invasions. This ain't it.
Rated by buyers -
I had expected analysis of potential warfare itself, but there is no concrete example for war scenario. The authors provide lists of weapons we may use and types of alien's purposes, then they suggest construction of an institution to prepare the war. I had rather wanted to read something between them.
Also, I had expect logical thinking for this book. If you also expect it, I can quote typical lines. They claim that the following things must be prohibited for members of the institution:
-drug abuse
-alcoholism
-sexual harrasment
-excessive speed in car
-cheating on taxes
I recommend you to read the other reviews below for more examples of their "logics".
Rated by buyers -
As other commenters have noted both the editing and the science behind the book are sloppy and careless. The strategies and tactics for defending earth have not been well thought out. A section of the book amounted to a paen to governmental secrecy and why the authors think it is important. And to why the government should give large amounts of money to aerospace companies and lie to the people about it.
Some interesting ideas, and might be worth buying for about a third of the price.
Rated by buyers 
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An Introduction to Planetary Defense
I remember the stars. No, I remember the promise of the stars--the promise of a future antiseptic and soft around the edges. A promise shattered by the hard reality of the arrival of the Overlords. Now, my days are filled with pain and torment. I labor from dawn to dusk, scrabbling across the harsh desert, imploring the dry earth to give rise to the stark monument demanded by the Overlords to symbolize their power and prestige. I'm but a slave, and according to our masters, a slave requires nothing but work, food, and religion, but I require something more. I require hope. No, I require retribution. I grab a rock. Its rough texture fills my hands. It fills my heart. "Bless this rock, oh Lord. May it crush my enemies' exoskeleton..."
I grew up reading and loving science fiction, and I love reading about aliens. Any story from aliens-are-hungry and coming-to-eat-us, to earth-needs-to-be-demolished-to-make-way-for-an-interstellar-superhighway, but I always found these books in the science fiction section. An Introduction to Planetary Defense: A Study of Modern Warfare Applied to Extra-Terrestrial Invasion is, just like its title says, a book discussing possible events in case an extraterrestrial invasion force one day appeared and started attacking Earth. But it's not a work of fiction.
Nope, the authors are dead serious. The authors, all highly-educated experts in their fields, decided to apply serious science to the matter of defending earth from an alien invasion. They start from the perspective of probabilities. These guys have done their homework and have done a nice breakdown of the "Drake equation", which Cornell astronomer Frank Drake developed for estimating the number of probable civilizations in the Milky Way. They've done the math and according to the "experts" there's a very good probability of at least one ET visit in the course of the average earthling's life span.
Hmm, since mathematics isn't my strongest subject, I'm not going to check their work. But I am familiar with Fermi's paradox, which is the apparent contradiction between the high probability of extraterrestrial civilizations and the lack of evidence or contact with such civilizations. You know, just where is everybody? For a great book on the subject, check out If the Universe is Teeming with Aliens...Where is Everybody? Fifty Solutions to Fermi's Paradox and the Problem of Extraterrestrial Life by Stephen Webb. It gives 50 hypotheses on why we haven't found empirical evidence of probes, starships, or email from little purple men.
Ok, so it's a pretty big universe, and there's at least a possibility that we aren't alone. So what are we gonna do about it? Well, just because the authors are paranoid, doesn't mean ET isn't out to get `em. SETI(the search for extraterrestrial intelligence) is basically beaming radio signals advertising "Hey, we're over here". They might as well put up a neon sign that says "Eat at Joe's". Face it, the chance for ET being hostile is at least equal to him being benign and showering us with great technology--such as can openers that actually work.
The authors examine modern warfare and how we might possibly implement our ability to wage war against a significantly advanced alien force. They used various fancy force multipliers and simulations, to come to the conclusion that ET would kick our [...], and that in order to have any chance of survival, a reserve force (the general population) and asymmetrical war (guerrilla tactics) would need to be harnessed to have a fighting chance. These guys motto is "prepare now, survive later." So, it may come at no surprise that they support a big military budget on such things as space lasers and powered armor. I get the impression that these PhDs just want to blow stuff up in a really big, expensive way.
There are also some attempts to examine invading motives of aliens. The human race knows only two motivators. These are 1. Desire for gain and 2. Fear of loss. Aliens may want slaves, food, or just to pick up earth chicks, but the thing to remember about aliens is well, that they're aliens. I did find how mankind might react to an invasion an interesting section. Will we believe it? How will our beliefs and response aid or hinder the overall defense of Earth? Will religious, moral, and ethical beliefs influence the decision-making process, and what are we going to do if the aliens end up looking like demons, or cute, fluffy bunnies? For a more complete look at this fascinating subject, I recommend Contact with Alien Civilizations: Our Hopes and Fears about Encountering Extraterrestrials by Michael Michaud. His analysis suggests that contact is a serious - and not necessarily pleasant - possibility....
Whatever you wish to believe, I have to give the four authors credit for some serious chutzpah (courage bordering on arrogance, roughly equivalent to "nerve") for writing this book. The book did leave me with some thought-provoking questions, and I recall the axiom of my history teacher, "those of you who fail to learn history, will be doomed to repeat it." It brings to mind the Native American tribes of the New World. Surely, if they had known what the white invaders had planned, they would have never granted him a purple card? Hmmm...maybe the surest sign of intelligent life in the universe is that they haven't tried to contact us...
Kevin Coolidge, editor "Of A Predatory Heart"
Comments, questions, let ET phone home or hold an alien autopsy? The cat wrote a book, Hobo Finds a Home: A children's book about a barn cat who wanted more out of life. Illustrated by Susan M. Gage written by Hobo.