Yes, another mini-book review! The Perfect Edge by Ron Hock is just too good not to mention. It's beautifully published, and goes into more detail than any mortal woodworker needs to know about the sharpening process as it relates to edge tools. Ron Hock has become obsessive about mastering the perfect edge over the decades, yet he is able to distill this information into an enjoyable read.
Metal has always baffled me; how can it become softer when heated, and then become harder when heated? Why does it get softer when you bend it, but then get brittle and break when you bend it? Within a single chapter, Mr. Hock explains more than I ever knew about metallurgy all at once. I really feel like I learned more in about an hour's reading than I had ever learned in my life about what steel is and how it works. This chapter alone is worth the price of admission unless you happen to already be a master metalworker.
While telling you all you need to know to obtain an obsessively perfect edge, the book also gently lets you know how to determine "good enough" for your needs, and reminds you that the important part is to get back to working with wood... that's why you're sharpening in the first place, isn't it?
I picked this up on a recommendation from Chris Schwarz when I asked him for a good metallurgy introduction. His suggestion was spot-on and it bears repeating, so go ahead and pick this one up if you haven't already!