Wow. After two listens, I can say it's brilliant but I still feel like it needs to sink in a bit more. The final song is likely the worst on the album and Celestial Tear was stuck in my head after two seconds of its chorus. Also, Tobias Netzell is probably my favourite harsh vocalist after Mikael Akerfeldt.
Before I begin I'll say that Celestial Tear for some reason just sticks in your head after the first listen. I'm not really a fan of death metal but this is excellent. In Mourning finds a perfect balance in mixing melodic riffs, clean vocals, progressive metal, and death growls. Every song on this album is excellent, even as you converge later in the album the songs don't get stale or boring. I would rate this a 5 but I've read many reviews on line that state that In Mourning sounds like Opeth. I've never listened to Opeth and until I do I won't know if they are a knockoff off of the metal legends or they are a band creating excellent music. Either way, I feel fine in rating this a 4.5.