Well I've tried manually syncing at least two dozen times and loaded another book, but I'm still at 144 MB total space. How odd that it flipped out on your device.
BTW, I HATE that carousel and the suggested books. Those who keep saying there are no ads are full of it. Suggested books to buy are nothing but subtle ads, period! Amazon really sucked up the app now. (And yes that supposed to be an "s".) I can no longer get the Time left feature to work in personal docs. It worked in 4.2.x.x. Oh well, no biggie, I use the iPad Mini 2 for reading now. Oh, and still only one freaking font on the Android app, WTF Amazon!!