>The first odd thing I experienced was the inexplicable feeling that there was someone else in the room during my meditation. Luckily this didn't disturb me too much, one of the books I had read at that time mentioned that this was something that could happen during zazen. I now know that it is called the sensed presence effect. Other sits were more pleasant - I often had a sensation of uncaused joy arise. Sometimes I would see intense and clear images inside my head. During one session I saw a bright blue humming sphere that I knew was God (or some kind of representation of) - I swear I could hear the harmonious hum of it. I had previously abandoned my Christian faith but that experience alone made me reconsider my stance.
I've been trying to meditate on and off for years, including daily 30 minute sessions for months at a time, and never experienced anything remotely as intense as this author. In fact despite all the time I've spent trying, I can't say I feel like I've gotten any better at it. At best I've developed a sensation I would describe as being extremely tall, as though my head were posted thousands of feet above my legs, but psychologically I don't feel like I'm doing any better today than when I started with respect to observing my thoughts or focusing on, say, breath.
I suspect some people are far more predisposed, be it nature or nurture, toward successful and deep meditation than others.