"The old sourcebooks for the Forgotten Realms setting often used the conceit that they weren't fiction, but rather in-universe documents that had been handed to TSR or Ed Greenwood, usually by Elminster. Since in the fiction of D&D, modern Earth exists and Elminster and Ed Greenwood are friends, and also Elminster likes German beer and Monster Energy. The conceit of Volo's Guide to All Things Magical, for example, was that the titular work was originally published by Volo, but that it was full of misinformation and just enough fragments of real magic to be extremely dangerous. To its readers and everyone around. So Elminster hunted down every copy and destroyed it, and released his own, re-edited Volo's Guide to All Things Magical to drown out any surviving copies of the original. At least one of which ended up in TSR's offices to be republished on Earth. The introduction to the book explains this in-character as Elminster. Other sourcebooks are said to be assembled by IRL writers from the original in-universe sources. Empires of the Shining Sea, for example. In the prologue, writer Stephen E. Schend recounts how Elminster kindly provided 16 tomes and a dozen scrolls and several maps on the topic of Calum Shan by dropping the heavy bundle on top of him while he slept. He also laments that he'd warned Ed Greenwood against giving Elminster access to sticky notes, because now, quote, every 400-year-old document is ragged with little yellow notes."