It has helped me attain the deepest level of meditative state, where I am almost aware of my consciousness as a separate process from the constant sensory input. Becoming an observer, empty-head.
On another level, I've found it very settling in times of emotional turmoil.
I did have a near panic attack from the book when he makes somewhat of a case that both hemispheres of our brains might be independently conscious, with one permanently silenced as control of the body is held by the active one that controls our body. A prisoner in someone else's body, literally, with no way to interact with the world. It is pure physiological horror. But alas I cannot do anything about (other than try to talk to that other entity and see if it can trigger some sort of response?) so no use getting worked up? The world is full of day-to-day cruelty and it's not my fault.
If "you" are setting out to converse with the neighbouring regions of your brain, which in my experience is a worthwhile endeavour that does pay off, it'll have to be through visualisations, symbols, images, daydreams, imaginings.
Like any adult language-learning, there are a bunch of practice exercises before you're ready to converse in vivo. As a way in for you: first get a bunch of spare attention through your meditative practice. Then use it to work on visualisation of familiar places like your house/neighbourhood until you can move around fluently. Repeat with a request like "find something red" and notice when a part separate from your monologue locates it without effort/searching. Then start making broader requests for imaginary landscapes or situations and see what replies you get. Be a kind, accepting, fearless conversation partner. Look for surprise and speed as markers of authentic responses from elsewhere than your monologue.
Do you have any further reading or information on communicating with the other hemisphere?
This was some two decades ago. I've never felt anything like that after that, but the memory of the sensation is still very strong.
No drugs. Just the most basic 'lie-down-relaxed-and-watch-at-a-dot' exercise. And wham.
It was pretty cool. I was an adolescent back then and I had decided several years before that logically religion was total BS. Had I been religious I'm sure I would have interpreted my experience as being in direct communion with God. But, I interpreted it as a neurological response to my meditation - which did not make the experience any less spiritual.
The experience did not reveal anything new to me, but it made me feel the truth that we all are one and connected, philosophically speaking.
Feeling is something purely logical discourse seldom provides. This experience was pure feeling. Like, I intuitively feel my legs are part of me. I felt the whole world was part of me. Now, this is at the same time true - or - false. We are made of the same atoms and are interconnected through our actions and the laws of physics. At the same time, it's a bit silly to describe oneself extending beyond ones body. So, one can choose was I enlightened by a fundamental truth or was I just a bit silly after a brief session of neurohacking.
So, I suppose the key here is the personal experience.
I'm sure there are a lot of ways people can have deep spiritual experiences without them interpreting it as communicating with divine forces.
The one thing I am tying to validate / invalidate is weather "spiritual" as used by non religious people, is mere hacking of our delicate physical and chemical machinery.
I don't know, but I have a gut feeling the spiritual awe one gets from one religious sacrament or another and getting it through other means are the same thing.
Effectively, the way I see it, religions claim something that is universal and publicly available as under their domain. It's like a guy came and wanted to resell the air you breath back at you.
Similarly I feel drug afficionados are sometimes overselling their hobby as the one key to the mysteries of the universe.
I don't mind if someone is religious or likes to do drugs. What I don't like, is that one or another claims something that can gained by other means as belonging to their dominion.
The major religions are especially intransigent and arrogant about this in their creed - claiming things that belong to all men and women to belong only to one sect or another - thus poisoning themselves doubly by first trying to fool those outside of their creed, and then being intellectually dishonest of their own experiences.
It really is, if our minds are entirely a manifestation of the brain.
Is it just the perspective of the one who has the experience? As Tim Leary said: The caterpillar cannot understand the butterfly.
We all carry around a default metaphysics -- a deep belief structure about the nature of reality. It is possible to transcend these beliefs in a way that allows you to grok (not just understand) that they're not supported in the way we normally assume. That transcendence is often accompanied by an overwhelming gratitude, joy, awe, and wonder that are normally inaccessible.
Of course, our belief structures almost always come rushing right back, and so we interpret the experience in terms of our metaphysics ("oh, it was just brain chemicals"), but part of us understands the sense in which this is just a story.
During "the inaccessible," assumptions about an objective or pre-existing reality fall apart as well. From within the standard materialist metaphysics it seems rather unlikely that we're special (or that meditation even does anything "transcendent" besides jiggling around some neurotransmitters).
It's different from psychology as it doesn't try to explain / cure things like child development, depression, bipolar disorders or most of the other multitude of subjects that psychology works with.
Some people have already posted his insight meditation which is worth trying. (Maybe try a bit of more basic breathing meditation first so you realize how distracted you are getting with your thoughts before trying - you will likely get a lot more out of it if you can keep your mind from jumping around).
I would say the difference with psychology is that psychology is based on external observations and predictions, while "spirituality" is your own internal experience. They are completely different.
While I enjoyed reading it and it helped me make sense of a lot of things related to meditation, mindfulness and spirituality in general, I can't say I felt every other sentence was highlight worthy.
The chapter on spiritual frauds was however very enloghtening.