INVISIBLE INK by Brian McDonald

Don't let the thin spine and small number of pages fool you.  Brian McDonald is a straight-shooter and economical with his words - but the ones he uses are suprisingly visual; his examples are on the money, and with each new paragraph I had a lightbulb go on above my head.

To purchase or download a copy, click below:

http://sh.st/n2LVg

You definitely need prior knowledge of writing.  This is a book aimed at writers who have a few thousand pages under their belts, but for some reason feel stuck at the pivotal points in their stories. 

Highly recommended, I re-read it once a month to keep me on track.