For an initial adventure; and especially one they are attempting to tie storywise across multiple games and books, I do not think sandbox makes sense. (Also, there's no Monster Manual. This could pose a problem for a sandbox game. I would not be surprised if the MM is still being worked on. )
Really the term railroad is a bit derogatory. And not really very accurate. A railroad implies that the players have no agency, that they can’t do anything not specifically laid out for them in the adventure. Adventure path really works better. A path can fork. You can leave the path and come back to it later. Yes you have an eventual destination, but what you do on the journey is completely up to you.
Steve Winter said:Things start out straightforward enough in Hoard of the Dragon Queen, as you’d expect in a low-level adventure, but by halfway through, the Dungeon Master is making almost as many crucial decisions as the players are. The Rise of Tiamat asks a lot from DMs right from the beginning, with its immense background events, political component, and multitude of paths for characters to follow to their goal.
I’ve tried more traditional sand boxes in the past, but they don’t really work out for my group. For one, they want a story. Exploring and finding cool things scattered around or traditional dungeon delves don’t really do it for them. They want some kind of external motivation. Goblins attacked the town, we need to go investigate. The Princess kidnapped the dragon, we have to go rescue it. The gate to hell has been breached; we have to go plug it up.
When I tried a sandbox with story threads like that scattered around they would latch on to one at a time and see it through to completion before looking for another. So in effect it was no different that if I had just presented them with a single story one at a time.
All of those are scenarios not stories. Adventure hooks rather than complete adventures, and nothing in the sandbox mode of play prevents using them.
I think Murder in Baldur's Gate and Legacy of the Crystal Shard both did a decent job of being published sandboxes. The sandbox was partially an illusion in that there were 3 different plot paths that you could bounce between and were interwoven to some degree. However, they still came together in a finale regardless of the path you took. They were not true sandboxes, but they allowed the players to lead the plot progression..
I'm quoting Tormyr but this question is addressed to everyone: Are there any other really good sandbox published modules? I'm currently running my group through the Caverns of Thracia, which is a kind of sandbox in that it is an enormous dungeon that can be explored in many ways, but I'm looking to move to a larger scale outdoor sandbox when they're finished with it.