Murder on the Eberron Express is a 6th level one shot adventure. It looks like it can be played in 3-5 hours with a small or large number of players. This is a great introduction to the tone and flavour of the world and the authors of this product do a fantastic job of setting up everything you need to succeed. This adventure reminds me strong of Murder on the Orient Express meets Baldurs Gate version fo Betrayal on the House Hill. In my book, these are all wonderful things that will bring people who enjoy aspects of these items to the table and give them something to enjoy.
This adventure does take some prep work for both the Dungeon Master and the players, so make sure to plan ahead and incorporate time into your session to allow for that. There is some oppurtunity for combat in this scenario, and due to certain circumstances - this may be more difficult for your players than average. You will also want a system for passing notes or delivering messages between the players and the the DM.
One word of caution: This adventure may pit one player's character against another. Make sure to cover PVP etiquette with your players ahead of time.