"I have heard so often about the mystery of "I AM" -- what is so mysterious about it?"
Dear friend, if you do not see the mystery and the wonder of "I AM" then it would be hard to appreciate the miracle called 'YOU.' When you refer to yourself, ordinarily, you refer to name and form such as "I am John." However, this "I AM" prior to name and form is everyone's "I AM." In fact, every living human being says the same "I AM" except that they refer to their ego instead of their true identity of "I AM." It was Jesus who said that the great mystery is how Christ lives in each heart. All 6 billion humans are the very same "I AM" that you are! Can you see this incredible mystery?
You, in truth, cannot die because you never existed. How and why? -- because you are "I AM" which is Existence itself and never had a beginning. It was never born.
Now the mind gets boggled through this until you start 'seeing' with your heart that you are not a body and name which Albert Einstein referred to as the great optical delusion of mankind. You are a hologram and not made in linear time from which your brain functions. In other words, the creation of form was the result of duality. Duality has to be in creation to survive and linear time was born to create that illusion. However the truth of you is holographic which also means that the time you seem to be living now has already been lived and you are going through the motions. Holographic means that the smallest pattern is the same as the biggest pattern. The smallest seed or fragment contains the entire universe just as one single cell of your body contains the whole image of you physically. In fact it has been proven that one single cell of your form can create a duplicate of it.
This mystery is beyond the mind but can be felt in the awakened spirit. You are the timeless now that is not locatable but seem to be localized in time and space. This is the mtsrery. To 'yourself' you seem to be so alive and real and yet so does everyone human being on earth feel the same...and yet it is all ONE. Now ho can you understand this with your mind? Isn't this a mystery? Yet all this is a fact, it is the truth and the only Truth.
Here below is a video that can give us a greater glimpse...