Let's say I ask someone what did you do yesterday and they answer with I read a book yesterday. Does that mean they read the book till the end? If so, then how do I say that I read a book, but I didn't finish it?
I have asked this question too and you will probably get different answers. As far as I know "I read a book yesterday" means you read the entire book. You could say: "I did some reading yesterday", "I read a book for a while, an hour, etc." or "I read a few pages or chapters", something like that. I prefer "I did some reading".