to be completely honest, i haven't studied too much Kabbalah (don't know how to spell it in english either).
Kabbalah is actually rather old, but quite as old as the Gemorrah and other commentaries. It's basically a huge "what if" writing. For example, in the creation of earth, it says that woman was created twice. The Kabbalah said "Hey, what if they were talking about two seperate women? Well, she doesn't show up later, so she must have been kicked out of eden. And who fathered caine's children? Hmmm, it must have been that same woman, as there was nobody else in the world at that time." And thus, the story of lilith was born.
As for how widely accepted Kabbalah is, most rabbi's wont teach it to anyone under a certain age (i think its mid 20's) as it supposedly will drive younger, weaker minds insane.
Too much what ifs for my taste. The original 5 books of the Torah are my favorite religious doctrine. Murder, genocide, the fall of man, the invention of murder, incest, its a pretty intense book.