CORRECTION: Calibre 3.29 does not install cleanly on Raspbian. My earlier/above message from 2018-08-14 was erroneous, as 3.29 had been installed on top of 3.28 then, leading to fake news (or certainly a false positive!)
Sad Reality: the dependency errors of installing Calibre 3.29 on Raspbian (on Raspberry Pi) are worse than May/June/July:
calibre : Depends: python-pyqt5 (>= 5.11.2+dfsg-1+b1)
calibre-bin : Depends: qtbase-abi-5-10-0 [virtual package related to libqt5core5a] but it is not installable
Specifically:
installing package python-pyqt5 from repo debian-testing no longer functions as a sufficient workaround — as had helped back in June/July
