What does 这个书包看起来不大 mean?
起来 in this case is used as an adverb. It is combined with the verb 看 together as a phrase. 看起来 means looks as if. The people who is saying this sentence may not really look inside the volume of that bag, but only guess it would be big enough for carrying things, or fit someone's figure.

You can also make some other phrases in the same way, such as 闻起来 for "smells", 吃起来 for "tastes", etc.


"这道菜闻起来很香". This dish smells delicious(but might not tried yet).
"这道菜吃起来很香". This dish tastes good.


In such cases 起来 has nothing to do with the meaning get up.