A lot of people think you have to read slowly to "let it all sink in" -this is a huge misunderstanding!

why speed reading works
the average "thinking speed" is around 1200 images/minute
the average reading speed is around the 225 wpm
If you read slowly, your mind will probably "get bored" and start all kinds of other processes in the background, and before you know it, your minds starts to wander off....You flip through the pages, but when you snap out of it, you have no idea what you've just read.

Why do people read slowly?
If people learn how to read, they learn to read out loud. And in this way, they learn to read at the same rate they speak. They get accustomed to a low reading speed.

The five steps to speed reading
1. Sit upright and alert! 30% of the oxygen you inhale is needed for your brain, If you slouch, you mess up the supply to your brain. And, if you keep your head positioned at an angle, your equilibrium will send the message to your brain that it can go wander off and go to sleep.

2. Move your finger or a pen or something else(I prefer a marker) across the words, doing this instantly wipes out most problems with reading faster. Start the pen 1 inch after the beginning of the line, and stop 1 inch before the end of the line, your eyes can capture several words at once, in this way it's one eye movement less.

3. Read with a rhythm, try 1 line/second for instance

4. Match your speed with the text, If it's complex, read slower, If it's boring, read faster.

5. Before you read a book, flip through it once, from beginning to end and look at every page, this only costs a few minutes.

Good luck increasing your reading speed!
related:
http://www.xomba.com/speed_reading_reality_or_myth
http://www.xomba.com/speed_reading_site_very_useful