I have a couple of kids who are slow readers, so I did want to help them improve their reading speed. We did targeted speed reading practice. (I would not do this with Pride and Prejudice right now. I would pick a novel unrelated to a current school assignment.)
This is the method I used. I had them start with 1 minute intervals of reading as fast as they could, stopping after every minute and re-telling what was read in order to ensure comprehension was being maintained. I had them do 1minute re-tells for about 10mins total. I had them keep track of the the approx length of each 1min passage. We did this daily until they had significantly increased their 1minute passage length. Then we continued the process for 3-min intervals for a total of 15 mins. After those passages significantly increased in length, we moved on to 5 min passages/re-tells for 25 mins.
After my kids have done this for about 6 weeks, their reading speed has improved substantially.