Comparative Mythology by Jaan Puhvel, probably.
It works with the myths of India and Iran, Greece and Rome, of the Celts, Germans, Balts, and Slavs to reconstruct an ProtoIndoEuropean origin.
Note that most mythology scholars focus on one area (i.e. Greel), and when they do "comparative mythology" they usually stick to IndoEuropean mythologies, or foreign "influences" and "origins" of their own regional area of expertise.
Once you start to include the Middle and Far East, and then African and American mythologies the danger of overgeneralization in your comparative work rises exponentially.
Comparative mythology of the IndoEuropean usually aims at reconstructing the Proto IndoEuropean religion that started it all, Indo-European Poetry and Myth by M. L. West is a great, recent work on the subject.
"Comparative religion" typically deals with present, currently practiced faiths.
Here's the mythology bibliography, which focuses mostly on Greco-Roman myths but also includes psychoanalytical, structuralist, IndoEuropean comparisons, etc:
http://pastebin.com/17BuEyuqIf you need names other than Jung and Campbell, famous people in this field - that are not in the psychoanalytical-symbological tradition - are Georges Dumézil, and Claude Lévi-Strauss for structuralism, their works are cited in the bibliography.