What is the difference between dot hack GU and dot hack GU plus?

.hack//G.U. is a video game series consisting of three games (Rebirth, Reminisce, and Redemption) that can be played individually but work best when all are played in sequential order. They are for PS2.

.hack//G.U.+ is a 5-volume manga series created before the actual release of .hack//G.U.. It is meant to sort of follow the plot of the games, but has some significant differences (such as events happening differently, and its continuation after the point at which the games ended)