In the form of speed-reading in which I was trained, you write a one-sentence summary of each paragraph as you're reading, and after you read a chapter or section, you review each of your one-sentence summaries. In theory this allows you to "process" things like textbooks into knowledge stored in your brain very quickly. In practice, speed reading only works for me if the material doesn't contain any concepts that I don't already understand.

I find it very useful when I need to get the gist of a paper to decide whether I want to actually read it in detail.