Writing a book and where to start

The book that everyone talk about writing and the people who listen to this kind of detail. Where do you start, what do you write about, how do I write my first book?
These are some of the questions that come up time and again. Bookmarks are not big enough to explain, not to me anyways.
Books are good if you like reading, if you are finding it hard to read the chances are even if you do write a book its not going to be a very good book. More importantly why should anyone read it?
So you book may need to be about something important that answers a few simple needs. In essence with this in mind you could write a book everyday for someone else to read. So the trick has always been to read and rereading.
If you are writing fiction the chances are not the influence comes from what is in front of you. I understand. Perhaps you would be better versed in freelancing, musing others and reshaping online. A pen name can be a great way of writing reality. Someone else’s reality presumably. Then there is an old adage of pen or typing, speaking seems to be far less cumbersome. However does anyone find the time and understanding to create the characters?
One other persons reality for experienced writers is exciting because of making history seem better than reality. No one other than agony aunts seem to publish reality. And even they have articles written by people who are stuck and wish to overcome difficulties. The papers publish these stories under particular categories, they probably even proof read and edit before printing.
The reality I would like to read about is much more mundane and may require a manifesto rather than a place to be put. The category of boring, illiterate, day to day chores and savings not really cut the sides.
Am I then suggesting an autobiography or diary, I am not to sure?
Does this book then require photographs of how you see the world taken in a style like a voice similar to where you want to be. Or is it something more gratifyingly all about you and your audience as a legacy? A book to spawn a legacy, or a homage to the things that you think bring you happiness and joy. Writing a book is no mean feet and at the end you will then be categorised, pigeon holed, annexed from any other choices your future could comprehend.