1. If there was no Holy Book (Bible or any other) we would no nothing about a magic man in the sky. However, some wise and cunning businessman would eventually claim to know all the answers.
2. First off, I do not believe in god. I do think, however, there is a difference in your analogy. For example, if a manual to build a tv stand has quite a few misprints, it is still useful to keep it because you can figure out the kinks on your own. Although its unreliable to put your complete faith in the manual, you can still find it usefull if there is nothing else provided to help you out.
And its for that reason that many hold onto the bible despite its unreliableness, simply because they feel its still usefull and there is nothing else to build thier faith upon.
The sad thing is with the example of the manual, how many times have we put something together WITHOUT USING THE MANUAL? In my case, all the time. Although I've had to go back and redo it or take it apart again to fix an error I've made, I take a certain pride in not using the help provided. And how many times have we looked at the manual or instructions and truly thought it was a magical code in a different language?
The same can be said about the bible, although many find it usefull, in the end, if they would just open thier eyes and reflect on thier lives, they would see that it was THEM who ultimately put their lives together, for good or for bad. I truly believe that people would have so much more confidence and love for themselves if they stop giving credit to an imaginary being or a Holy Book and give credit to themselves, like when you put together a TV stand!