[What comes first] The Blurb or The Book?

How many of us imagine the blurb on our newly published book covers before we've written the book? I know I have. 

I have also written (several) ever changing synopses. I think this has helped, however, I can't help but wonder if I had been the originator of The Bible, where on Earth would I have begun to write the blurb?....'In The Beginning' I guess. Ever curious, I gave it a go:

As the only child to a single mother, the boy had a thing or two to prove.

 Too big for village life;he left to go out in to the world to make his way, all that his mother asked of him, was that he believed her when she told him he was the son of God – a big ask – but being somewhat full of himself and his overblown sense of worth he went along with her fib.

Making his way around the world, well a small part of it, I don’t think he ever came to Sussex, he spread joy and performed miracles. Turning water in to wine (Penn & Teller made a man cry milk which was more entertaining) and feeding 5000 people with only five loaves of bread and seven fish (could’ve gone to Iceland). Making friends with a lively bunch of lads who called themselves The Disciples life was looking up. 

Nothing could have foretold the horror that was to come.

No, I totally agree - not good!

It does, however, prove one thing, that you have to truly believe in your story and to know it inside out and back to front before attempting to write that all important attention-grabbing, appropriate blurb.

A synopsis, however, can be a work in progress up until the moment you let it go to a publisher. 

I know that since beginning my novel I have changed the plot completely and that it has evolved from a memoir of childhood to a crime/suspense, which has come as something of a surprise even to me! I started with a character, something like my younger self, and ended up listening to this little girl who has taken me on an adventure that I, in my widest dreams, could never have taken as a child. She still has pieces of me in there somewhere but her life has taken a whole new somewhat sinister road.

Try to write the Bible blurb, in any style and share it here.