Shim...RabbiO has referenced a well known mainstream intellectual who also as a rabbi and a man has deep faith. His work Sacred Fragments is well know and highly recommended. It speaks more to those who are looking to find their way back to their roots and deepen their spiritual connection to God. Rabbi Gillman's work on the afterlife is trying to explain esoteric truths from the standpoint of when mainstream Judaism first began to refer to them...as in implying an immortal soul and an afterlife, as in refs in Daniel, Ezekiel, many of the Psalms, and so forth.
And he is also trying to make these concepts accessible to a modern Jewish audience, many of whom had no exposure to Jewish thought on reincarnation or the afterlife in their Jewish education, because it was considered mystical to the point of being "fringe". So he's done an admirable job of bridging a gap..or a chasm. This perpective is relevant to many...especially those who may not be that religious or even spiritual...but you may also want to look at some other angles.
The esoteric truths of the afterlife are of a similar tradition to Kabbalah...largely oral for who knows how long (?), until it "broke out" in written form in Spain. These writings were traditionally discouraged (and still are in some sense) for study by ppl (men) who had not reached a certain stage of learning and maturity. So it makes sense that it was rarely referenced or touched on in the Tanakh.
Also Judaism's focus has always been on grounding the soul in this life and then reaching "up" to God. We won't finish the task (of perfecting the world) but neither is it our place to desist from it. So the emphasis was never on the next life but on the current one, as it's all we have. Also known in buddhism as "living in the now".
Having said all that, as RabbiO mentioned, the Chasids are I think probably the best source of straightforwardly mystical writings. Though I am more in line with R. Gillman's tradition because I'm a woman and there are one or two important things that I disagree with re: orthodox positions...still, I
highly recommend Rabbi DovBer Pinson's work on the afterlife. There is not a drop of Christianity in here, but what is there is nonetheless IMO both Jewish and also very universal.
I have seen both Rabbi Gillman and Rabbi Pinson speak at conferences. Both are very good but very different. I will say that you want to understand the Jewish perspective from a deeper or more mystical perspective, I would
definitely seek out Pinson's works.
http://www.amazon.com/Reincarnation-Judaism-Journey-DovBer-Pinson/dp/0765760649
http://www.jewishwisdomafterlife.com/
Cheers!
7L