https://www.mobileread.com/forums/sho...ght=constantia
That is an EXCELLENT thread with ALOT of recommendations, many of them seconded and sometimes thirded (is that even a word). Some of the common themes as far as favorites in those threads, which will give me a starting point for testing are:
Georgia
Fontin
Gentium
Droid Serif
Chaparral Pro
Minion (someone specifically mentioned the pro condenssed medium)
Arno Pro
Garamond Premier Pro
Scala