I watched the movie and then read the book.

I tend to prefer movies as a storytelling medium, and enjoyed watching the story unfold that way. I ended up just wanting to know more about things that were implied in the movie but not explained, and the book filled in those gaps well.

So if you want to do both, and want to get something new when you do each, then, having done it that way, I would recommend it.

Edit: reviewing my app history, it took me somewhere between 10-11 hours to read the book, and I do not read fiction especially fast.