Just finished reading Self-Editing for Fiction Writers. This is a fantastic resource for any author who is struggling with editing their own work or looking for some new knowledge. Written by two professional editors who have been through many a slush pile, it contains excellent advice about the craft using examples that are clear and easy to follow.
The examples are the strongest asset, as they are in context of actual works, not just one-off sentences like many editing and grammar books use.
Highly suggested if you or someone you know is deep in revising that manuscript.