The type was small and hard to read. He did not bother beyond the first few words if he did not think it useful. There were a great many forms of wandering spirits, and it was curious such a thin book should have so much to say on them.

This Iron Race, book one

Dr Claude Crabtree, writing in 1930, suggested this apparently casual remark alludes to the common belief that books of magick, as opposed to books about magick, were panaceas, literally ‘all things to all men’ and could, in effect, answer any query given to them regardless of its obscurity. From the description of the book Bheathain reads it seems unlikely it is anything other than a simple guide to common magickal practice and phenomena—genuine books of magick being rare and expensive—therefore, accepting the remark is without obvious narrative context, we concur with Dr Crabtree it probably refers to a text outside the narrative.

MacGregor wrote considerably more on the nature of books of magick in his last major work; The History of Scottish Magick (published posthumously in France in 1899 as L’Histoire de Écossais Magie) and this brief extract may be of interest:

Ordinary books suffer from a requirement to contain in one volume all that reasonably falls within the remit of their title. Thus, even books of seemingly modest scope weigh heavily in the hand and by their length obfuscate and conceal the seed within an immensity of chaff; notwithstanding the uninteresting chaff will contain one or many seeds suiting the enquiry or enquirer of a different time or place. Books of magick, necessarily containing magick need not suffer from this but may reveal to the reader exactly what he sought (whether he knew it or not) without the pain of always carrying and periodically winnowing the chaff. That books of magick go to such pains to please the reader may be the reason they become curmudgeonly when treated in a careless or unappreciative manner.

This Iron Race, book one

How such books might materially function is another matter entirely. The best explanation argues they are palimpsests with multiple layers of writing any one of which may be superimposed to suit the needs of the moment. Hendryk van Zelden, a man whom, despite our disagreements, we allow is an excellent communicator, has said in an interview that books of magick are akin to the hyperweb in containing a vast amount of immediately accessible knowledge whose exact whereabouts and provenance are almost unknowable.