quiet reading

[Ju]

'quiet reading' means reading by heart without making a sound. Am I right?

Ju

[JohnParis]

I would say that quiet reading is the opposite of reading out loud.
Quiet reading = read silently to yourself.

[SoothingDave]

It could also refer to the setting. If someone told me they planned on doing some quiet reading this weekend, I wold figure they would curl up next to a roaring fire and enjoy a nice book. The scene is quiet. No TV blaring, no kids screaming, etc..

[emsr2d2]

I might think someone was going to the library to do some quiet reading.

We don't call it "reading by heart", by the way. Perhaps "reading in your head".