Here is a good
speed reading test. It measures both reading speed and then comprehension, and it has a better comprehension test than similar sites.
I am a VERY slow reader, just 180wpm, but I also have a VERY high level of comprehension 90%.
I've tried speed reading and just don't enjoy it. My comprehension also goes way down, but the websites all claim better comprehension or at least no loss in comprehension .