Because sometimes you have to stop reading The Odyssey on the Metro so you can annoy the other people on the train by taking pictures and giggling loudly.
Sometimes Serena hides behind her book and looks angry, but really it symbolizes how Odysseus hid behind his beggarly disguise near the end.
And then when I hit myself in the face with the book, which is what's happening here, you see, it means "oh, the trials of man, they continue to hit me in the metaphorical face...with their...poignancy and their hard covers."
Serena searches the Metro tunnel for monsters (just in case).
The Metro ride was approximately 10 years long but I did not anger any gods or kill any Cyclops, so I am ahead of Odysseus already.