I was a liberal arts major, math was never my strong suit and I have had to struggle with many of the concepts here, reading and rereading them to understand what the author is saying. It has  been well worth it though because as I begin to understand what is being said, I find it absolutely mind blowing. I have heard the phrase "spacetime" in the past, had even read a couple of explanations which left me feeling like the village idiot, but Greene's writing makes it comprehensible. I feel I have a pretty good grip on relativity and special relativity, if not with the actual constructs, then at least with the analogous examples.  I am only 100 pages or so into the "Elegant Universe," I have to read some and then stop and digest it before moving on, but moving on is something I plan to do.