Wide-ranging and filled with scads of information that would take you years to duplicate on your own: stuff like which color order to mix glasses in during a melt so they don't go opaque, piles of information on DIY molds and furnaces, lots of obscure details that would be incredibly frustrating to sort out yourself. Plus some of the DIY processes in here are so brilliantly crazy it's worth reading just for them: building a cullet-and-frit-maker that can turn bottle fragments into sorted powder, that involves a garbage disposal and a shopvac. Can you *imagine* the glorious noise that'd make? Pretty awesome.