This is a great adventure. I have just finished running it for my players and they all loved it.
I do not usually use premade adventures, prefering to create my own, but this one caught my eye. I believe that adventure RPG sessions should be like action/adventure blockbuster films where the director has an unlimited special effects budget. It is rare to find an adventure that is suitably "cinematic".
The Iron Giant is exactly what I was after in an adventure. The author(s) set out to create a story that was literally larger than life and they more than succeeded. What's really great about thiis is that the adventure is for 3rd level characters. It proves that you do not have to be 15th level to have an heroic, even "epic" adventure.
The only down side is that the organisation could be a little better. For example some of the maps are in the front of the book and some are at the rear.
In summary, if you want a grand, rollercoaster of an adventure than this is it. If your 3rd level characters want to hunt goblins and scavange for silver bits then perhaps they would be better off playing something else.