It wont do anything if you shoot with RAW. I dont use it. Probably good to use if you are not a serious photographer who hates processing photos and shoot with JPEG.
In camera sharpening is very crude, inaccurate, and is done to each image globally. I recommend disableing it.
Sharpening effectively is usually a 3 step process: capture sharpening (done during Raw image dtat file conversion, not in the camera), local sharpening, and output sharpening. Sharpening for print is done differently than sharpening for electronic display.
Most of those books were actually written by Bruce Fraser. Jeff helped Bruce as Bruce's health declined.
Bruce was a founding member of PixelGenius LLC, the company that first produced software that could produce UnSharp Masking (USM, or sharpening) effects on digital images. Unsharp masking - Wikipedia, the free encyclopedia