as mentioned, it's believed Dragon Magick was founded by D.J. Conway [not a great source of knowledge to say the least] but like Wicca, it has evolved and has become very personal and spiritual. dragons are astral beings who practitioners can call upon for guidance and strength [much the same way a spirit guide or deity would] http://www.fox-moon.com/dragon.html is one of the best [and most common] sources to learn from. most information is verbally passed down through clans from dragons, and very little is written down, let alone shared outside the clan. i also wrote an article on some basics called 'Dragon Magick' and can be found in the Spell Casters rituals.
in terms of dragonology you're going to have to do a lot of research. dragons can be found all over the world. many don't appear like the typical european dragon, some [like the lindworm] don't have wings, or only 2 legs, some have feathers, wings, but no legs. it's long and complicated, but basically every culture has a dragon myth. for this reason some belief dragons were physical [like dinosaurs] but died out a few centuries ago. others believe they were physical but traveled to the astral. then there's those who think it's just some great story telling. research and choose for yourself.