How do I write about suggested reading by my professor
Don't obsess over the wording. "Thanks for the suggestion...interesting... following up". Your summary might be valuable if the professor hasn't actually read the paper and asked for a summary. 

But, don't get to deeply caught following "interesting" ideas that aren't related to your own research. If he is asking you to expand or redirect your research, then you need to have a discussion with him. That can be a serious matter. 

But a certain amount of this is normal. Your professor wants you to learn, but he also wants to speed up his own learning. That can be good or bad for the student, depending on how much it helps build a relationship as well as an education. 

You write better by practicing. To paraphrase another idea: Good writing comes from experience. Experience comes from bad writing.