Even if you haven't read any other post-finale Voyager novels, you can pick up Full Circle and go with few-to-no problems. All the important facts from the other four are covered. However, if you read Full Circle first, you're spoiled for the major events in Destiny. Because Destiny was published before Full Circle, the Voyager characters don't play that large of a role in the trilogy - the Enterprise, Titan, and Aventine are the major ships involved in them. So I'd recommend reading Destiny first.