From Shadow, Substance

This speculative work discusses how one might harness the Weave to turn an illusory object or creature into its real counterpart, with commentary and criticism from noteworthy Netherese illusionists. There's cautionary words from many of them about the ethics and implications of such magics, and it seems agreed upon that while the idea has potential, it shouldn't be encouraged.
Reading this tome gives advantage on Arcana checks related to Netherese illusion magics.