Will Bryan and Robert agree to disagree on The Here and Now by Ann Brashares? Only time will tell. 

Prenna James is a time traveler. Her, her family, and others from her time live on the outskirts of the present day after escaping from a future where a mosquito-borne illness has taken the form of a plague. Prenna and the others follow strict rules to never interfere with history, never reveal their origin, and to never, ever be intimate with the time natives. When Prenna falls for Ethan Jarves, all rules go out the window, and a race to stop a catastrophe is thrown into action.