Are you a fan of the Generation of Miracles? If so, then Last Game is a must-see, because it's basically a fan tribute to them and adds nothing to the prequel. Not only did it make most non-GoM characters look bad (skills-wise or personality-wise), but it also deviated from the parent manga, Extra Game, in an illogical and poorly-thought-out way. The "villains" were irksome, which is weird because KnB has always had a knack for creating sympathetic opponents - something they completely kicked to the curb here. The art style is different from the original (in a bad way), though the animation was good. Game play was pretty repetitive; you won't see anything much here that you didn't see in S01-03.
Tl;dr - GoM fans: go for it, this one is for you; everyone else: skip, it's gonna ruin the main series for you. Especially the bonds that certain GoM members had built up with their non-GoM teammates, which they've gone out of their way to look down on here, for no apparent reason.