Hello,
I do speed read. However I do not speed read exclusively.
The technique is not just about reading quicker through the material, that’s just the tip of the iceberg and the most popular/best known feature of it. First of all, it’s about setting yourself a time frame and an amount to read (like 1 hour for 1 reading). Then skimming through the reading rapidly, so that your eyes catch the big lines and some important/interesting concepts. Then stopping for a moment to make the connection between what you’ve just seen and what you already know. And THEN, reading the material at your rythm.
I guess that all the steps can be beneficial for everybody in order to get a clear idea about what you’re going to read and mainly, to make some connections in your head with already known concepts. It’s up to everyone how quickly/slowly they read. Anyway, reading once is not enough, at least for non-superheroes.