I too have always been able to read at what other people think are very high speeds. It started when I was in 2nd grade. (talking Australian here, don't know if this is the same terminology for other countries) In grade two I could read at a grade 6 level, by year 7 I could read at a year 12 level. This is by no means some amazing feat, I'm certainly not special.
It was around grade 5 I realised that I could actually read much faster than my peers. It was silent reading hour and I finished my book in a few minutes, the teacher told me that I hadn't and to keep reading, the other kids called me a liar. It was a long hour as far as I was concerned being a little kid. After that I hid my speed reading and only ever used it to entertain myself. I would try to see how fast I could read the subtitles on the Japanese shows they played on SBS, or to knock off an entire book before my mum made me turn off my lights. When I practised by myself I usually did it out loud, trying not to slur my words, stuff like that. Once again this was just for my own amusement.
Reading out loud I am very fast, my sister is the only person I have ever met that can understand when I read a passage at full speed. Silently I read many times faster. I always hear people saying that cutting out the sub-vocalisation allows anyone to read at high speeds, but I still say the words in my head as I go.
I find I can read most fiction without having to slow down to enjoy it, as well as still comprehending and remembering all the plot details, character interactions and even the exact wording of dialogue from fairly far back in the text. I find it is not as useful for technical writings or anything involving stopping to understand math. Despite this it is still very useful for quickly finding passages or words in large chunks of text or reading through material that can be learned by rote.
All in all I treasure my little skill and would be very upset to lose it.