I finished A Separate Peace, and, while it is weak at places, when it's good, it's excellent. See:

"All of them, except Phineas, constructed at infinite cost to themselves these Maginot Lines against this enemy they thought they saw across the frontier, this enemy who never attacked that way -- if he ever attacked at all; if he was indeed the enemy."

What a nice last line. It reminds me of:

"So we beat on, boats against the current, borne back ceaselessly into the past."

That is probably the best last line of literature...almost certainly of American literature, at least. I think every human alive would do well to memorize the last line of The Great Gatsby.

My personal favorite last line, however, is this:

"One bird said to Billy Pilgrim, 'Poo-tee-weet?'"