I write these books to take my mind off of all the crap in my life and the world around me. I feel at peace when writing, no matter how bad the book turns out, as I learnt in 4th grade when I wrote a book  about a talking pigeon whose best friend was a mouse.
Personally I think it doesn't matter how bad the book is as long as you as an author enjoy writing it and some people out there can enjoy it as well, or at least read it and find it interesting.