Thanks for the files.
I have installed the latest public version of FBReader 1.8.2 to my Sony PRS-T1 (Android version 2.2.1).
I also installed the latest beta version of FBReader 2.0 (beta 8) to Nexus One (Android version 4.3) under the Android emulator from the Android SDK.
In both cases, FBReader opened your Atlantis EPUB without a problem.
I cannot say why your friend cannot open EPUB files generated by Atlantis. But it is very unlikely that the problem is with the Atlantis EPUBs. Otherwise there would be plenty of complaints from other users.