I learned this using a simple technique: Start using your finger to track where your eyes are. Move your finger a little bit faster than you read. Resist the urge to go back if you think you missed some things, just assume things will clear up later on, or if they do not, they were not very important to begin with anyway...

After a while, you can stop tracking line by line, but just scan a page by moving your finger diagonally across a text. After doing this for a while, you can skip using your finger all together, and glance over texts to get the main idea.

I have been doing this for over 2 decades, and can glimpse at contracts for peculiarities by glazing over a page, or go through books taking only a few seconds per page if I'm in 'scanning' mode.

It's a nice party trick as well ;).

(Note that reading contracts for the first time like this are good for a first review and general flow, but you miss a lot of details, so you need to do a proper review later on.)

I tend to take a little longer when I'm actually reading a text thoroughly, although I prefer to read texts really fast and re-read them after a while when they are interesting or need more attention.

IME not all texts are readable like that; some text is very information-dense and it gets really hard to keep track of the context if you try to speed-read it.

On a side note, glancing over code/search results might have contributed bigtime to this skill as well.

The biggest "disadvantage" is that - when on holiday - I need a gazillion books, because it takes me at most 2 or 3 days to get through a single book...