1. Look through the book.

2. Read through the book.
(Are both the same? What is the opposite of the expressions?)

3. Look the book closely.
4. Read the book closely.
(Are these the opposite of the two sentences?)

1 and 2 don't mean quite the same thing. "Look through" means just paging through and looking at pictures or scanning a few pages. "Read through" means exactly that.

An opposite would be not reading it ... or even looking through it!

3 and 4 have the same issues -- "read" means just that; "look through" or "look at" means scanning or paging through, but not reading.