You're right. Both of them are used to nominalize a sentence and same meaning. 読むのが = 読むことが In English, you can say this sentence in a different way as below and they are same meaning as you know.　 ・ I like to read books. ・ I like reading books. Strictly speaking, 読むことが is more formal expression than 読むのが. I think 読むのが is a colloquial expression and more casual. Hope it helps ;)