How is the .hack series? I am interested because there were some characters from the series in Project X Zone which I played. Also how is the anime?
The quality varies for both the games and the anime series. The first set of 4 games is the original "main" story of the series, but the gameplay, while honestly isn't very good. The story is unique and pretty great though, and playing around in the pseudo MMO setting, trading with other players and reading the news and message boards is nice.
While you aren't left with many questions after it wraps up, the anime, manga, and novels fill in and expand the lore. Each one is both their own stand-alone story and part of the puzzle.
.hack//sign is the prequel to the games and the anime that most people are familiar with. It leads up to them, but follows different characters and centers around a different problem. It's... talky. Lots of panning shots and exposition, but the story is interesting. There's also an unrelated series of anime episodes that came with each game and covered what happens in the real world during each respective game. After that is a terrible non-canon anime adaptation of the games' lighthearted sequel manga.
There are several other anime of varying quality including a direct prequel to the GU games that IMO was pretty mediocre and spoils a huge plot twist at the end. Its events are more or less covered via dialogue in the main GU trilogy so I wouldn't recommend it. The others take place a good deal after the GU series and are self-contained. .hack//quantum is fun but is 3 episodes that are more or less their own thing.
