Recently I found this font called
Caecilia LT Std 55 Roman, which looks very nice to me, but I'd like to add some weight to it for use in Calibre Viewer and conversions to PDF.
At first, I succeded by using Fontforge -> selecting all glyphs with Ctrl + A -> Menu Element -> Style -> Change Weight. I was able to create a version with much more weight than I would like, as I used 10 "Embolden units".
Afterwards, I played with smaller embolden values, but the changes wouldn't seem to take. I've tried rebuilding font cache, uninstalling and reinstalling the fonts etc.
So I quit, humpf.