Well, first off I see if it's something a kid made in 10 minutes or if it's something somebody spent a lot of time on making and is actually aiming to help people.
Secondly, I look at how professional the thread is; if it looks good and detailed then that's another factor I take into action.
Thirdly, I look at the official reviews, official reviews are always something you should incorporate.
Fourthly, I look at the user's reputation, if he/she has any negative reputation that was about scamming, or something serious, then I wouldn't deal with them. I also wouldn't deal with them unless they have at least two people how +repped them.
Fifthly, I look at how trusted the user is.
Well that's basically how I choose whether to buy an eBook or not; but nowadays I never buy eBooks because I already have working methods that I created
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