"Metallurgy of Steel for Bladesmiths & Others who Heat Treat and Forge Steel" by John Verhoeven http://www.feine-klingen.de/PDFs/verhoeven.pdf An interesting technical introduction to metallurgy, without being overly tedious. Congratulations to the author, for what sounds like it could be a dry subject. I am pleasantly surprised by how ignorant I was about such a common everyday material, and about the fascinating changes that take place in the crystal structure of steel with mere temperature changes. I've got no plans to forge steel, or make blades, but found this book very good so far (although I have been interested in metalworking in general lately).

"Basic Lathework" by Stan Bray. This is the best of the beginning lathe books that I've been reading recently, covering the parts of the machine and accessories, techniques, and cutting tools. Very minimal pre-requisites.

"Metals in the Service of Man" by Arthur Street and William Alexander. A very light read about industrially useful metals, a little history about them, and their uses.

"Measurement" by Paul Lockhart. I finally got this book after reading his "A Mathematicians Lament" from a while back. https://www.maa.org/external_archive/devlin/LockhartsLament....

"How Round is Your Circle" by John Bryant and Chris Sangwin. Just started this, but it sounds interesting, the pictures are intriguing, and it pushes a lot of my "interesting" buttons.