If you want to read fast, a good vocabulary (and to a lesser extent spelling) is essential. Studies show that those with better vocabularies not only read faster, they also have better comprehension.
You can also look at it another way. Not knowing a word will dramatically slow down your otherwise fast reading.
If you want to improve your vocabulary and spelling there are lots of free and paid solutions available. eReflect’s vocabulary builder “Ultimate Vocabulary” is a popular solution. There is also a spelling software version of this product called Ultimate Spelling.
In terms of free solutions, Improving Vocabulary.ORG has some excellent free info that you can put to use right away. There are also lots of great vocabulary videos youtube.