Occult literature is full of interpretations and theories and commentaries by various authors. Were this not the case, Crowley wouldn't have had much to write about. We can take or leave these theories, but we should also remember that the Enochian system of magick has at its core a Christian understanding of mysticism and angelic mythology. It is certainly not orthodox Christianity, but Christian nonetheless. The same can be said of much of the magick we see as authoritative today: based in the Judaeo-Christian worlds of the old grimoires.
I am not a Christian and I do not agree with Tyson's theories about the Apocalypse, but Tyson is a quality author and knows his stuff (see the work he did with Agrippa's Three Books of Occult Philosophy as well as his own books). Therefore, I found his writing in this book extremely interesting and thought-provoking.
We needn't accept normative Christianity in order to find aspects of the Christian mythology interesting or helpful to our ritual practices.