For class, I was searching google images for drawings depicting impossible moons. I’m pretty sure this one wins because of its irony with the title. Note that I haven’t read the book.
#1 You can’t see a crescent moon with this orientation at night time, because the sun would have to be in the sky (i.e., above and to the right), thus making it day time.
#2 The star to the bottom left of the crescent shouldn’t be there due to occultation–the dark side of the moon is still there, blocking our view of that star.