How often do you read to your child? How many times per day? I am a working parents and I find it very exhausting after working and no energy to read books with my kid.

It's not so much the quantity of time spent, but the quality. There's no fixed timing. Once a day before bedtime is fine. You can also find other activities to do with your child, or just talk to him. https://www.washingtonpost.com/local/making-time-for-kids-study-says-quality-trumps-quantity/2015/03/28/10813192-d378-11e4-8fce-3941fc548f1c_story.html