Short answer - not always, not really, but I still read a ton, and in my humble opinion I synthesize that which I don't completely understand, at least a little bit, into a broader understanding of the world.

Longer answer and a story - I know I forget a LOT of what I've read. How could I actually remember all of it? Just recently, I got to almost the end of a book I'd read previously (I had forgotten I read it previously), without having even a glimmer of "Oh, I've read this before". And then, in the book, I got to a story, as opposed to some dry facts. The story was somewhat emotional, lots of detail-rich imagery.

Anyway, it was at THAT point, late in the book, that I remembered I'd read it before. Or rather, I'd come across that same story before.

What that really made clear to me was, the power of STORY. Telling a story, as opposed to giving some facts.