It is absolutely fascinating just how deep non-existence goes. It's crazy, even non-existence doesn't exist... and that's the final hurdle.
Ok, tell you what - there's two pieces of writing which really delve into this.
One is the Sutra On The High Seat Of The Treasure Of The Law (Otherwise known as the Platform Sutra)
I have repeatedly had my brain blown out of the back of my skull with that one. It's very detailed, and hits the thing from a lot of different angles.
Then I read the Diamond Sutra - which is shorter, and more focused.
It will take your mind and beat it like a ginger stepchild.
Truly, these things are two of the most powerful pieces of writing I've encountered.
You might also want to check out the Bhagavad Gita, the most holy text of the Hindu faith:
It's fucking mental, and contains an incredibly sophisticated and profound philosophy of the infinite.
You might also want to check out the Tao Te Ching, which is the central text of Taoism. An exceptional, and very beautiful piece of writing which is utterly destructive of mind-structures and thought-forms.
I really liked this one. It really undermines the conceptual level of thought.
I'd also throw out a mention to the Gospel of Thomas, a collection of the original sayings of Jesus. Don't worry, it's not religious. In fact, it's been deemed a heretical document by the Catholic Church. It's like the "James Dean" of the Gospels.
Joking aside it's an extremely interesting piece of writing which has some very challenging and jarring statements. A lot less 'moral' than normal Christian literature, and to my mind, all the more potent for it.
Ok - all these things are tools. Like the work of Tolle - it's not about filling your head up with all this stuff. It's about using this stuff to empty your head.
With all these pieces of writing what I'll do is read it until something strikes me as either totally nonsensical or completely profound. These are the two signs that an epiphany is lying just beneath the surface of your mind waiting to arise.
What I then try to do is dwell in that state of profound understanding or jarring rejection and just be there completely. Very often after a few minutes (or maybe a few days) of what I suppose you could refer to as 'contemplation', I'll get that 'breakthrough' and see shit from a whole new angle.
It's all very exciting if you ask me.