This is my thought too. Hey Amazon makes a lot of money selling content, so why not sell fonts or font packs too. I would be willing to pay $25 for a single font if it meant I could read for hours without eyestrain!

I'm the same on my preference for serif now that device screens have the higher resolutions needed to view them. I remember reading a scholarly article back in the 1990s where studies were conducted to see what worked best for reading on computer monitors. One thing the study indicated was that lower resolution (common on monitors in that era) made reading serif fonts much more of an issue than reading sans serif fonts. They found that people generally preferred serif fonts with printed material (higher resolution) but preferred sans serif fonts for low resolution monitors because of the decrease in eyestrain. But that is no longer an issue with most new devices as they tend to have a much higher resolution than the old 72 dpi (Apple) and and 96 dpi (PC) computer monitors.