The first time I encountered the Satanic Bible was in high school (1996). Another kid I knew had brought it to school for the shock value of it. I was too chicken shit to read it then. It wasn't until 2005 (25 years old) that I finally read it and had the same realization as you. A lot of time waisted.
I had a similar experience when I first read TSB at age twenty. I've mentioned this elsewhere, but it's appropriate for this thread. At that age I was too ignorant to understand The Satanic Bible, and I associated Satanism with being the polar opposite of Christianity, i.e "devil worship". I grew up being forced to go to a christian church. As A kid, I was called a "walking encyclopedia of biblical knowledge" by the minister, but I was never baptized, for I always knew something wasn't right about it all. I read the book, but I didn't understand it. It's a little embarrassing, but perhaps other people had a similar experience.
It wasn't until later, having gone out into the world and lived a little, that I understood how TSB reflected nature and the world as it truly is. I think that, when approaching Satanism, a certain level of maturity is important. After that realization, I read everything else that was available at that time, and I finally "got it." I remember that time very clearly. It was truly an awakening, and now I can't imagine myself not being a Satanist. Satanism permeates my life, my art and my dealings with others, and the full importance of that is now beginning to manifest itself. And, you know, it feels pretty damned awesome!