Here’s a useful virtual booklet about wood-engraving by douglas Bliss from a series of instructional pamphlets published by Dryad Press in the 1950’s.
Note: Perhaps the most rewarding way to view this wonderful booklet is in full screen mode. The toggle is found on the far right of the toolbar, right above this text. Other available tools allow you to zoom in or see an overview of all the content at once. Also, you can manually turn the pages by dragging their corners with your mouse.