Since this was too long for mod forum description, I'll post it here
This mod is actually a whole game in itself without any connection to the main BG2 plot. The first part of the mod takes you from Irenicus's dungeon back in time approximately 100 years to a small town in the Spine of the World known as Easthaven. If you have played IWD then the plot follows the IWD game from there with many new items and dialogues between NPCs. There is also a new optional kit for Imoen, which retains her original class as thief if you wish, designed specially for her, and three new joinable NPCs. The second part takes place after you have returned to and exited Irenicus's dungeon. There are three more new NPCs whom you can add to your party. Hrothgar's is the main quest/plot and is what NeJ is all about. Throughout the game he will take you into the past several times and also, into the future in order to complete his very important quest. There are many, many new areas to visit as well as those of Baldur's Gate. You will have the opportunity to gain new spells on the completion of mage specific quests and discover new items. All new NPCs come with quests of their own, and all come with their own weapons and items.