I have successfully cultivated a “third speed” somewhere between close reading and skimming, which is helpful for cruising through casual books like Robert b Parker novels , etc, but I still prefer reading slowly as I can visualize better and appreciate word choice, sentence structure etc when I do.

My advice is to just cultivate a wide vocabulary as that will help you out the most (each time you have to think about a word’s meaning slows you down, IMO, more substantially than a minor difference in the speed at which you cruise over words.)