New Etrian Odyssey: Millennium Girl is a reimagining of Etrian Odyssey that adds a story to the first person dungeon crawler. There are set characters to play as, but if you want a traditional Etrian Odyssey experience you can make your own party in Classic Mode.
Shigeo Komori, the director of New Etrian Odyssey, clarified Classic Mode is not a simple port and that the "new" gameplay features will be present in Classic Mode. New Etrian Odyssey: Millennium Girl has tweaks like Grimoires which let you learn skills from other jobs and even monster skills. There are over 200 Grimoires to collect. Players can also visit the Guild House to get quests too.
New Etrian Odyssey: Millennium Girl also lets people switch between old and new background music. And for people that haven’t played an Etrian Odyssey game before there are three difficulty settings. Picnic is designed for beginners that just want to see how the story unfolds. Standard is the usual difficulty and Expert is for Etrian Odyssey fans.
New Etrian Odyssey: Millennium Girl comes out on June 27 for Nintendo 3DS.