In the last few decades there has been a tremendous increase in the desire of people to learn kabbala, Jewish mysticism. Along with this there has also been an increase in the number of books available for such folks, both in English and Hebrew. Translations of the Zohar, both into Hebrew and English are readily available in Jewish bookstores and on-line. Some of the greatest works of mysticism can also be found in such places as Amazon.
Contrary to the opinion of others I don't think this is such a great thing. I mean, yes kabbala is an important and deep subject within Judaism. The problem is that kabbala is the neurosurgery of Judaism and, like neurosurgery, it's not something anyone with a particular hankering for it should be getting into, especially unguided.
This especially bears mentioning as we live in the age of Artscoll. Once upon a time a person who wanted to learn Talmud, for instance, needed a teacher. He needed to go to yeshivah for a course of studies and his learning would be guided by an experiences rebbe in order to ensure he got the appropriate understanding of the text. Nowadays with the availability of the Artscroll or Steinsaltz Talmuds this is no longer the case. Anyone with an interest in Gemara can go to a Jewish bookstore or even go on-line and purchase a set complete with decent translations and elucidative notes. On one hand this has opened up the world of Talmud to countless Jews who otherwise would have been cut off from our heritage. On the other hand it has created a culture in which the commentary in the book becomes the person's rebbe instead of a real live teacher connected to our mesorah.
This lack of connection can certainly cause problems with one's understanding and use of the nigleh Torah. There's a big kal v'chomer involved when it extends to kabbala and nistar issues.
Why does this matter? While the nigleh deals with both bein adam l'Makom and bein adam l'chaveiro the nistar side of things involves bein adam l'Makom on a far more intense level. It seems to me that this can be so intense that focusing on it leads one to forget about bein adam l'chaveiro.
This came to me a few years in a conversation with a Chabadnik who was telling me about how some folks had come through for him in a big way. I responded by asking how he had shown his gratitude. He shrugged and said "Look, it's all due to the Ribono shel olam. He's the only one we really need to show gratitude to."
This comment stayed with me because it really exemplified the attitude that exposure to nistar brings out in some people. Yes, God is the infinite, perfect and omniscient centre of our reality and the ultimate undeniable cause of everything. Yes, He has a personal relationship with each of us, even those of us that, chalilah, deny His existence. Yes, when it all comes down to it He is the only mover and shaker that truly exists. But that doesn't mean that He's the only thing in Creation that we should be relating to, that we should see our fellows as mere tools in His hands.
It is also clear from His words on the subject in Tana"ch that we should be seeing our fellows as important, that the need to interact with them positively is a definite virtue He appreciates. Far from ignoring the positive contributions of others to our lives because "only God matters" we are adjured to emphasize things like gratitude and kindness because this is the kind of decency He demands of us.
This then is the danger of kabbala these days, something which might explain the shockingly low level of bein adam l'chaveiro that is practised by many who otherwise claim to be on the highest level of piety. How many people strive to ensure their food is mehadrin min mehddrin min mehadrin but have no issue with theft and slander? If only God matters then other human beings don't and this is an attitude that we must all strive to avoid.