Concentrating on whether you understand or not is the most important thing during reading books. I had ever heard about the skill of "fast reading", so learned it and tried to read books as fast as I could.

The speed was fine, but I didn't understand most of what I read! This skill says that  you do not read with a voice or silent voice, you just use your eyes to scan line by line.

I think that words also contain voice information, if you ignore them, it's not a good idea, besides, I'm learning English by reading, pronunciation is necessary, or it will lack the opportunity to learn and practice the whole words.

Reading will speed up automatically if you read a lot and are familiar enough with the subjects you read.