This depends, but I try to read in a normal pace. Normal as in, not too fast that I couldn't read anything properly, but not too slow that it'd take me decades to finish something. I only read something slow when I have to understand them (i.e., philosophical texts, lessons at school, or a book I'm really interested in), and I only read something fast when I challenge myself or when I have to (i.e., quick reviewing, scanning and skimming notes). But when it comes to books, I always read in a regular pace and re-read when I want to understand and analyze something better.