Airborn by Kenneth Oppel. The book is intended for adolescents, but it is a really good adventure read! I liken it to Treasure Island or 20,000 Leagues Under the Sea.
It's a bit steampunk in that its setting in an alt-history where the airplane was not invented and so the airships predominate the skies. Massive airships, like Titanic sized. There are small ornithopters that flap their wings, but proper "airplanes".
It has air pirates, tropical islands, lost natural treasures.
It's a really good book in a trilogy about the hero, an intrepid young flyer named Matt Cruse. Matt is a cabin boy in this first book, but he moves on in subsequent volumes.
My 6th grader read it and loved it. I am reading it now and it is really good, regardless of your age! Especially if you are drawn to the whole airship setting (which I am)