Fact: there are a gazillion and a half writing books on the market. No, really. I checked.
So why in the world would I consider contributing more how-to bits of quackery to the literary pile of tips already out there? Hasn't everything about writing already been said, by those more learned than moi?
Honestly, this issue isn't any different than publishing another novel. Think about it. Every plot under the sun has been told, the only difference being voice and tone. That being said, there has and never will be a book on writing with my distinct voice and tone unless I put it out there.
And the same holds true for you.
Don't let the naysayers get all up in your business. No one can think or sound or write like you.
"A choir is made up of many voices, including yours and mine. If one by one all go silent, then all that will be left are the soloists. Don't let a loud few determine the nature of the sound. It makes for poor harmony and diminishes the song."
So say what you've got to say. Write what you need to write -- even if there are others out there on the market.