In Revelation 20:15 aren't those whose names are not in the book of life cast into the lake of fire to suffer for ever and ever along with the devil, beast, and false prophet?

In Isaiah 33.10-11, Isaiah said about Assyria:

Now will I rise, says the LORD; now will I be exalted; now will I lift up myself. All of you shall conceive chaff, all of you shall bring forth stubble: your breath, as fire, shall devour you.

 A careful study of the Old Testament prophets shows these expressions of the Assyrians being consumed by fire, and burned to lime are expressions of national judgment upon that nation. These expressions are similar to Jesus statement in Luke 12:49 that He came to send fire on the land of Israel. This is also the Old Testament basis for Jesus statement to the Jews in John 15.6.

Isaiah's language was also similar to that in Daniel 7:9-12, where Daniel foretold the judgment of the beast about to overcome the saints of the Most High. This scene portrayed the national destruction of the pagan power attempting to destroy the saints of the Most High. This is the same scene described in Revelation 20.11-15.

Both of these scenes depict national judgments against a nation(s) persecuting Gods saints, both have judgment scenes, both have people judged out of things written in the books, and both have those not pleasing God in the judgment being cast into a river or lake of fire. This national judgment goes with John's expressions of imminence in Revelation 1:3 (the time is at hand), Revelation 22.6 (things which must shortly come to pass), and Revelation 22.10 (Seal not up the words of the prophecy of this book: for the time is at hand). 

Those who take the early date of Revelation (A.D. 67) often believe these words refer to the destruction of Jerusalem, while those who take the later date for Revelation (A.D. 90-96) believe these words refer to the destruction of the nations who rise up against Israel when Satan is loosed from the pit for a season. Whether they refer to Jerusalem or the nations, they refer to national judgment(s).