Here's a interesting tidbit.
The regular Caecilia and Condensed version of Caecilia are the same font. I loaded then up in Word and there is no different between the two. they are the exact same size. So the Kindle must use some sort of special settings to get it to display differently.
So I took Caecilia Condensed and Scaled it down 5 percent and now it comes pretty close to displaying like the default version. Line spacing is off but I always though the default line spacing was too much. I didn't change any metrics. Just added weight and scaled 5%.
I really like reading with it.
I added a screenshot of the two. Original one left and modified version on the right at size 5.