It's not the size of the boat...
Ground Zeroes is an odd little quasi-preview for MGSV proper, which provides one real story mission (which will last around 2 hours at most), as well as some fun side missions and extra audio tapes and such, serving as the sort of Tanker chapter to Phantom Pain’s Plant chapter. The missions themselves are very enjoyable, particularly the main story mission, the extras are fun and the visuals are fantastic. It’s the reimagined Metal Gear gameplay that steals the show here though, the versatility of Snake’s moves and arsenal allow for a creativity in approach that I’ve not personally been able to find in any of the other games in the series. Very short, and perhaps released as a stand-alone title for business reasons rather than artistic ones, the game is nevertheless very fun and essential for anyone intending to play The Phantom Pain.