Actually it doesn't seem to work that well with a 32Gb card either.
I guess it's not the size, but another issue.
On reboot sometimes it just doesnt' mount the card (or maybe it takes a WHOLE long time to mount). Repeated reboots sometime fix it, sometime not.
The whole device is very slow as if trying to do something w/ the card, but I have no idea what.
Unfortunately when the device is in this situation, also the other, internal, card doesn't get mounted either, which means I see NO books at all in the library
Such a frustrating device, lot of possibilities, but ...