All depends on the context....
There is a place on the first floor to the right hand side as you enter. There's also a microwave and sink. Most of the time if I'm eating non-hot and dry foods its fine as long as you don't make a shit ton of noise that disturbs other people. I would also recommend against eating in the quite area unless its like a snack; and on top of that if you wanted to eat within the library try to go to the seats in front of the stairs or the area between the two areas of study (the place with glass and its facing directly towards the city and has sofas and whatnot).