The important thing, so far as a theist is concerned, is keeping you from not thinking about your 'faith' rather than thinking about it and finding it worthless.
Take, for example this ludicrously inaccurate, anonymous 'review' of my book, Ten Reasons To Lose Faith: And Why You Are Better Off Without It.It was almost certainly posted by someone who isn't interested in truth since there is not a word of truth in it.
Recycled banal arguments already refuted by scholars. Don't waste your money on this junk. The book has many errors both in grammar and content. This author uses a fake name and plagiarizes other atheists. This book is poor scholarship and offers nothing new. The conclusions that she comes up with are illogical and based on anecdotal inferences, not logic or reason. Over 90% of the book is meandering and doesn't make any points. The reader will get bored and will realize that this author is an amateur and has no academic credentials.
There are of course, no plagiarisms in it since every source is clearly identified and credited. Run it through an online plagiarism checker and you will find none. It's possible though that the 'reviewer' doesn't understand what a plagiarism is and can't distinguish between a credited quote and an uncredited one. After all, if they think simply stating that all the argument have bee refuted by scholars make it so, they are probably not overly endowed with critical thinking skills. It's noticeable that they don't attempt even a token refutation of any of the arguments. It's questionable whether they actually read and understood any of them, uncomplicated and well supported though they are.
By contrast, look at the reviews by people with no vested interest in misleading potential readers, some of whom are not too ashamed to reveal their true identities, as the above reviewer seems to have been:
This is an interesting book, but the author wrote a little more than I thought necessary in the area of documented scientific discoveries. 4 Star. (US site)
(From the UK site)
This is a cracking read from the author of the Rosa Rubicondior blogs. If you aren't familiar with them then I would suggest you rectify that. Faith is a pernicious thing, and this book shows nicely why it is better to let go of it and walk away. Religion is a drug, and faith is its pusher, binding people more and more closely to religion. Read the book. It says it all better than I can. 5 Stars.
Ten very good reasons. Easy to read and clearly written. 5 Stars.
[Update 24-05-2016] This just in:
Rosa does it again! This is an excellent book that looks at faith from a factual scientific angle. The author is a fine writer, and her articles are always a pleasure to read, whether it is on science, religion, or how they engage with the rest if us. If you are a fan, this book is essential reading. If you come new to these writings, you can also sign up to her blog which will be emailed to you if you want. I strongly recommend that. 5 Stars.
So, all I can suggest, if you want to discover what makes a theist go online and lie to you to deter you from reading this book, is that you read it to find out, then ask yourself why, if the arguments for religion and for 'faith' are so good and so strong, this 'reviewer' thinks it takes lies and deceptions to support it.
In fact, reading the book should hopefully give you an insight into what it is about faith that can induce this odd behaviour in its sufferers. This reviewer's comment should certainly raise that question in your mind.
[Update 3 June 2014] As of this date the abusive, defamatory and inaccurate 'review' has been deleted following complaints from Amazon customers. There is no way to tell if this was done by Amazon to protect their customers from this sort of misleading review and abuse of the starring system or by the 'reviewer', embarrassed by the universally hostile comments his 'review' attracted from those who had actually read my book. The same 'reviewer' wrote the glowing, even fawning and adulatory, 'review' on a 'book' by 'Sacerdotus'.