Nice idea...although how popular it would be is another matter. Gary has made some very valid points, some people expect (demand?) an answer to their question - usually within milliseconds of posting, and this is where forums come in...can you imagine them leafing through a book to find the answer?..most don't even have the patience to use the "search" feature on this forum
Again, a book only reflects the opinions of the Author! - I have read several D.J related books...some made me sleep within 20 mins of picking it up..others kept me awake until the Morning! - but sadly all had one common theme - they read more like autobiographies than an informative piece of literature (I did, I do, I am, I worked here, I would play this....).
If you do write an E-book then try and avoid over plugging your self, some of the previously mentioned books are nothing but excuses to impress or name drop (So I said to Steve Wright.......). Try and make it informative but not read like a School Text Book or a Haynes Manual.
Again..how much interest you would have, especially where spending money is concerned is another matter

you could always try selling it on E-Bay