Recently this book about barbarian films came out!
Besides the two official Conan movies (Conan the Barbarian and Conan the Destroyer) there are also reviews on sword&sorcery exploitation made in the ´80, mostly in Italy . The book´s name is "Sword and sorcery in cinema: Conan and other barbarians: A filmic guide" and you can find it on Amazon (available as ebook and also paperback), here is the link:
https://www.amazon.com/Sword-sorcery-cinema-barbarians-filmic/dp/B089CL1G6M/