>>5654229ok well here is the thing. first of all its not really a series so dont get your hopes up for that. most of the stories are disconnected. the mythos itself was worked on by several different authors, however it began with lovecraft. lovecraft had a writing circle where he shared his ideas for monsters with a group of people because the monsters themselves were not the reason for the stories. they were just a catalyst to get his themes across such as nihilism, atheism, forbidden knowledge, inherited guilt and what not. personally this is where i believe the mythos is strongest, because it had those very dark themes for a specific purpose. when lovecraft died the mythos was then picked up by august derleth. here he included very heavy jeudo-christian themes (because he was christian himself). and he focused on more of the theme of the monsters more than anything else. he managed to get lovecraft's work popular, but his writings were not nearly as good. he changed a bunch of unnecessary things just to support his christian ideologies. so to answer your question:
at the mountains of madness
the shadow over innsmouth
the color out of space
the dream quest of unknown kadath
the dunnwich horror
pickman's model
nyarlathotep
just to name a few. and stay away from any rpg or board game rulebooks. its just convoluted shit that has mixed in all the terrible mythos with the good. unless all you care about are the different monsters, then be my guest. but the very best of the cthulhu mythos come from lovecraft.