The manga tells the story different, but overall I read it to see the true ending. If you watched the anime, you can read from the chapter 42. In the manga, Yuuko sister was the Akihito instead of Asagi, that's the main change I think.
Though the ending of the anime is as good and emotional, but in different way.
Tasogare Otome X Amnesia is kinda special in that it somehow has a LOT of fanservice without it feeling like it's detracting from the very good mystery and romantic plots. I really recommend the manga and the anime which has the distinction of being an amazing adaptation that really translates everything from the manga even if the ending is a little different since it was made before the manga finished.