One of the things I picked up from "How to Read a Book" (where they put forward that speed reading is usually just bringing slow readers up to speed), is that not everything is worth reading. There is so much to read out there, that you can't possibly read it all (relevant: http://what-if.xkcd.com/76/), and you have to pick and choose. One way to weed out what is relevant is to apportion the correct amount of time and attention to each thing you read. Some things deserve none of your time and attention; others may merely require a once through skimming to get everything of value out of it. Other works you may never exhaust (HtRaB's authors posit that only great books fall into this category, by definition). Perhaps much more important than increasing the speed of reading is developing the skill to be discerning in what and how deeply different texts should be read.
Most informational books are packed with examples and context. Sometimes you need that stuff, but other times you can get 90% of the information you need just by reading the introduction, table of contents, and chapter conclusions.
I think it's important to understand your motivations for reading, and then choose a method that best fits your intended goals.
Reading is like eating — sometimes you want to savor a book and other times you want to grab and go.
