I like to mention books I love here. Sometimes those are writing books, like E. M. Forster's Aspects of the Novel.
But today I wanted to mention Amy Einsohn. She wrote The Copyeditor's Handbook: A Guide for Book Publishing and Corporate Communications. It's a brilliant book. Like my copy of Chicago, my TCH barely ever closes, and it's crammed with bookmarks.
Hence Amy Einsohn and the Making of The Copyeditor's Handbook.
And here's a list of distance courses in editing. :> Note that Amy teaches them for Editcetera.