if you want to learn more of Cthulhu, just read the Complete works of Lovecraft.
I would suggest you start with a short one like Dagon, but eventully you should do yourself the pleasure of reading The Call of Cthulhu.
I like the game of Cthulhu alot and enjoyed a couple Lovecraft works, specifically the film "Dagon." I have yet to read the book for Call, though I plan on it. I just have massive respect for anyone who can put that much detail into something. There are no shortages of cool here... I just made the assumption I was disliked.
This one was a thought I had for a while I am very much intrigued by the works of H.P.Lovecraft regretfully the only story I have read thus far is the call of Cthulhu but I am hoping to read read more enjoy Great Cthulhu!