I'm about halfway through "A Princess of Mars" (Edgar Rice Burroughs). I'm trying to keep my spending under control, so I'm working through anything that's public domain and therefore free on Amazon or iBooks.
Recent not-public-domain free titles (complete with lack of copy editing) include:
"The Phoenix Conspiracy" - Richard L. Sanders - read more like a romance novel than SF, and some really interesting ideas about what from our time will carry many centuries into the future.
"Spinward Fringe" - Randolph Lalonde - really epically long, interesting premise (characters are VR gamers who hack into a military training simulation and are then recruited and given their own starship) and more or less good plot. Some slow parts, some confusing bits, but overall I wanted to keep reading it so I guess that's a good sign?