Yes, iTunes audiobooks are encoded in protected M4B or M4A audio formats, which can not be playable on Android devices. As you know here, to download iTunes audiobooks to Android, we need to convert iTunes audiobooks to common audio files. But the tool I'd like to use is DRmare iTunes Audiobooks Converter from https://www.drmare.com/drm-audio-converter-for-mac/ , which can not only convert iTunes audiobooks but also Audible audiobooks to MP3, FLAC, WAV. AAC, etc. for better playback on Android. Have fun with audiobooks!