For what it's worth, I tried the Moby Dick epub3 on my PB IQ.
- The PB reader opened it, displayed the cover and... Nothing else.
- FBreaderj just crashed to its own version of a screen of death.
- Aldiko 1.x imported it cleanly and started to open it. It then choked and said the file was DRMed, corrupted, or the battery was low. Right.

- Overdrive added it to its library and opened it and it worked fine. No TOC, as expected, but otherwise no issues.
- Coolreader 3 likewise found no TOC but performed fine.
Next time I have nothing to do I'll try it on the PB360.