Embed fonts in epubs:
https://www.mobileread.com/forums/showthread.php?t=61587
Just be aware of the tradeoffs.
- If you want your files to be universal to any device then you have to modify each and every file. But, once done, they will use the font on whatever device you view them on.
- If you use a universal style sheet on the device, you don't have to modify any epubs, all of them will use the font specified in the style.css. The drawback is, as you already mentioned, they will only use the modified font on that device.
For me, I use a universal style sheet. If I ever trade my Sony for another device, then I would have to go back and modify each epub if I didn't like the default font. Of course, if I went the other route, I would still have to go back and modify each and every epub. I literally have thousands.