Re: Reading critically?
Asimov once said, if memory serves, that as his own career began to grow, he found he had the same problem of losing the carefree enjoyment of reading (not that he ceased to enjoy what he read, but he began to see it more and more with the writer's eye rather than just the reader's). I think that's true with most writers who have been at it for a while.
Reading critically is particularly important if you want to improve your writing; and if you want to do this, part of the program must be to read the best writers as well; not just what entertains you, but what has stood the test of time. One thing you might try is to read aloud; see how the words flow; note the cadences and how they change from expository prose to dialogue, or description, or what-have-you. Go back over things which particularly catch your eye, either positivel or negatively, and try to see why they made that impression.
Compare the best writers with those which are (or have been) most popular; those who set a trend in some field or other; look at how they develop ideas, how they handle the subtleties of characterization, plot, atmosphere, and so forth. Look for their abilities to suggest rather than baldly state; how ambiguity can actually enhance the power of something, and how it can also dilute it when done improperly.
And it doesn't hurt to get a book or two on the subject of reading critically and see what various techniques are offered, as well....
Reading speed... that is a sore subject with me, I'm afraid. As a reader, I had quite a high reading speed (e.g., I could, and did, finish off The Hobbit and LotR together in three days); but as a writer and critical reader, I learned to take a good deal more time, to force myself to take things slowly and consider what it was I was reading... and I'm afraid I've known people who learned to "speed-read" who could never do this, and consequently have lost out on the mass of what good writing has to offer as a result....