The one thing I have done to improve very small lettering is to go through the process of changing my lettering from a raster letter to a vector only letter that is eventually center lined. (basically Corel outlines your letter with a hairline vector and then fills it with raster to create a solid letter) You can only get so small with that approach. For what that is worth. Changing it like this is tedious at best. But it does help with small stuff. I would hate to have to do this with a teeny tiny copy of War and Peace however.
900x600 80watt EFR Tube laser from Liaocheng Ray Fine Tech LTD. Also a 900x600 2.5kw spindle CNC from Ray Fine. And my main tool, a well used and loved Jet 1642 Woodlathe with an outboard toolrest that helps me work from 36 inch diameters down to reallllllly tiny stuff.