You might check out
this thread about one option to speed up your reading a little. It seems like I read a little faster by reducing my column width (increasing margins) and don't lose out on any of the reading experience.
As for speed reading in general, if you are reading for fun, my thoughts are to make sure you don't turn reading into work. When I actively try to read for quantity I know I lose a lot of the
reason that I read - the enjoyment of reading. So just be careful.