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Rick Riordan: Percy Jackson and the last olympian (Paperback, 2010, Penguin)

The greatest monster of all, the storm giant Typhon, is on the loose, wreaking havoc …

Review of 'Percy Jackson and the last olympian' on 'Goodreads'

Like others have said, this final book doesn't bring anything new but it is a wrapping up of bits from the first 4 books. So often series leave things hanging or unexplained so I think it's a satisfying enough end. I'm glad there will be other books in the same world.