Very disappointing purchase.
The section on rune metals could have been expanded to the level of detail that various magics have. Where is the metal, how is it found, some measure of context and story. More differentiation of general categories of enchanted and unenchanted rune metals. As it stands, the category of rune metal appears to lack cohesive form as a species of thing. Some unenchanted rune metals have magical effect, some do not. In a consciously Bronze Age setting, far more should be done to detail the power of metal.
The additional spells lacked context with an example being the additional runes associated with Invisibility compared with RQ Role Playing In Glorantha. Looking at the Summon Ancestor spell, it and the tables are not significantly different from the spell as presented in RQG. Rules for illusions, highlighted as a selling point, are not different from that of RQG. As has seemed to be the case for many supplements for this game over the years, it is often the same information repackaged and resold.
Finally, the artwork requires some commentary. Partial nudes may well have a place for art critics and historians to discuss their merit. These materials are commonly possessed by under aged children and in other contexts their promulgation would be reasonably considered something to be controlled. Editorial decisions being what they are, I find this particular decision by the game creators to be troublng.
This would be better released as a more comprehensive treatment of Gloranthan magic that may or may not be forthcoming (Gods of Glorantha reboot?). If that is the case, spirit magic should encompass one book, rune magic one book, and sorcery one book with an additional book including detailed culturally relevant magic items.
Would definitely not recommend buying.