Arcane Lore itself states in its Introduction that it is "extremely speculative and subject to great changes" - more so than any other book in the Stafford Library. In contrast GRoY, FS, MSE, HHP, and Heortling Mythology (sorry for the abbreviations!) are deep background but not speculative and unlikely to be subject to much change.
>
> Jeff:
> > In the case where a Mongoose product contradicts something in the
> > Stafford Library, it is wrong and the earlier source correct.
>
> Including Arcane Lore?
>