Basically just watch Blade Runner. 
Only if it's better than the book. The book was pretty terrible.
The book wasn't that bad. I thought it was one of his better ones.
And it is only loosely based on the book. No Mercerism at all.
I found DADOES to be the bad sort of a rambling read, creating far too many plot points and concepts and leaving most of them completely unanswered (or answered in an unsatisfactory manner), before ending in a fashion that made me wonder what exactly the point of the entire mess was.
It had its good points, but I never felt attached to any of the characters and I can't see any way in which my life was bettered, or made more interesting, for reading it.