I think in the last thread I had just mentioned that I was ordering the Annotated H.P. Lovecraft books. I have now ordered both, and while I received the second first, and they are all relatively short stories, so it shouldn't matter which was read first, it DOES matter. So I am now reading the first annotated edition of H.P. Lovecraft's stories, including the Call of Cthulhu and At the Mountains of Madness. These stories (in addition to a few other shorter stories) really describe the ideas and thoughts of H.P. Lovecraft, and give a person a firm grounding in the Great Old Ones and other mythic beings. Reading these stories has given me a huge amount of insight into the games my DS1 and DS2 are playing.
Of course, Dh and I are into D&D; we have been since long before we met and long before we had children. Our kids have taken to the game greatly, and both DS1 and DS2 DM their own games with friends (while Dh DMs at home). However, reading Lovecraft has made me realize the similarities with the many video games the boys are familiar with, especially games like Bloodborne and the Witcher.
I highly recommend HP Lovecraft's stories to anyone who would like to better understand references to Cthulhu, R'yleh, the Necronomicon, etc. in games and modern parlance.