 If you liked
.hack//Sign
|
 ...then you might like
Noir
|
+ Both have some mystery, that should be revealed at the end. That mystery has certain name - "Noir" in Noir and "Key of Twilight" in .hack//Sign.
+ Both have beautiful OST from Kajiura Yuki.
+ The style of art is similar.
+ The tempo is almost the same.
+ Both have two realities in the show: everyday life and mystic world of past (in Noir); everyday life and cybernetic world (.hack//Sign).