How to write a book and then Sell it?

Most of the writers claims that a book idea can come from anywhere. From a travel experience, from your home, from your neighbours, from the guy working in the next cubicle, from a girl travelling in train with you (I doubted this but Chetan Bhagat claims this for his boon one night @ Call centre), from a guy sitting and chatting with you in a restaurant (I don't know how many people are there in the world who is going to start a conversation in some restaurant and end up giving you a book idea but some people claim that in the preface of their book). It could come from the gutter which never stop stinking, from politicians the size of whose bellies is directly proportional to the ministry that he held now (or have held sometime back), from the policemen who always ask for a bribe (even for lodging a FIR), from the firefighter whose firetruck was always in the thick of the action (bloody why he didn't ever ask for a transfer), from my bathroom from your bathroom or from bathroom of the neighbour, from your pet dog, cat, rat, rabbit, cow, monkey, donkey whatever pet you like, from the family of Bhahadur Shah Zafar who never got his share of money back from East India company, from history (always at the receiving end as nobody is there to sue you), from that poor girl whose husband went to Dubai for 2 years yet she became pregnant after 15 months, from the door delivery guy, from your college life (yeah! this thing is catching up fast and poor thing is that everyone is making bucks out of it). In short, an idea can come from anywhere for example what about google? Good enough right?

But well, this gentleman has crossed all the boundaries and came up with this wonderful idea of writing a book about the world's top ten books (first question mark). Well at least he had this thing in mind and ended up compiling a list of some 500+ summaries (making the life hell a more difficult or easy it depends actually). The author claims that it's pick of the world's top 125 authors (another question mark) and he has done a lot of number crunching to arrive at the final list of top ten books in different field (3rd Q. M). Anyways writing is one thing and selling is other and guess what works best in selling your creation? Simple answer yaar, no idea only controversies. Let people put question marks at-least for the answer's sake they will read it for sure. Well whether it sells or not, it has given a new hope to poor writers who can now look forward to google for a subject.