Reddit mentions of Ariadne's Clue: A Guide to the Symbols of Humankind (Mythos: The Princeton/Bollingen Series in World Mythology)

Mythology is awesome - most box bookstores (like B&N) have at least a small mythology section where you can get your hands on original sources like The Prose Edda and such. Joseph Campbell is pretty popular and whoever owns the rights to his work keeps cranking out reprints of his lectures, so those are usually good too (sometimes they sound too "self-helpy" though). Anthropology (particularly folklore) dips into the same vein, so people like Ruth Benedict are good to read too. I'll mention a couple of things that might pique your interest as well, since you won't usually find them on reading lists.

• If you like the theme of universalism among myths and how those symbols reverberate in the human psyche, try Anthony Steven's Ariadne's Clue. Steven's draws from Jung to make an analysis of mythological symbols and tropes in those stories.
  
  
• Some scholars feel like myths embody a prehistoric awakening of sentience and intelligence - basically that these stories are early blueprints for what makes us human. If you're interested in that, try The Origins and History of Consciousness (Erich Neumann, the author, was also a Jungian and heavily relies on archtype theory in this book).
  
  
• For just a good read, try The Songlines by Bruce Chatwin.
  
  
• If you're curious about myth construction, try Roland Barthes Mythologies. It's actually pretty accessible compared to the stuffiness of other academics and philosophers, and focuses on modern myths.
  
  
• Oh yeah! If you like Grail lore (the holy grail and Arthurian studies, which is more about legends than myths I suppose), Jung's wife wrote a book about it. Which I still need to finish. (ugh)
  
  I love mythology so I'm always excited to hear people talking about it.

>Where do you recommend to study symbols??

It depends on what symbols you seek clarity and understanding of? Symbols are replete in myths and fairytales, in the occult, religion and art, mysticism and metaphysics. Immersing yourself in material from those regions will give you access to a comprehensive collection of symbols and symbolic content.

This relates to what Jung called amplification, though in his case that was employed in a therapeutic context.

There's an essay on the Purpose of Amplification here,

an archive of symbols here,

and their publication in a book here. Perhaps the archive and book in particular could prove useful for your needs?

Alternatively there's Anthony Steven's book Ariadne's Clue: A Guide to the Symbols of Humankind?