The Iliad is an epic poem attributed to Homer and dated to the 7th or 8th century BC. It's also the first book you read in Literature Humanities. Freshman in CC are informed that they're supposed to have read the first six books (chapters) by the time they've arrived on campus. Many students actually do this. Others don't. Seeing as this is in preparation for a 1 hour introduction to Lit Hum lecture during NSOP, it's not likely that the professor is going to perform a reading check in an auditorium full of 1,000 students.
If you attend an Academic Advising Session over the summer before you arrive, a representative of the Columbia College Alumni Association will be on hand to present each member of the incoming class present with a copy of The Iliad. It's a gift made on behalf of the alumni of Columbia College, and a symbolic passing of the torch to a new generation of Columbians. It's a pretty cool gesture, though perhaps a little unrepresentative of the way things actually work at Columbia (cold, mechanical, and impersonal).
If you aren't able to attend a summer session, have no fear. You'll get your copy of The Iliad in the mail, or on campus when you arrive for orientation.