The album is splendid and an absolute beauty. Quickly became one of my favourites, up there with Imaginaerum and Oceanborn. This being said, it is not an easy album to digest and people might not like it at first. It is progressive, experimental and the composition of the songs do not follow some general patterns so it might be weird on the ear at first. I don't know how to explain it properly. The first disc, which contains 9 songs has the exact amount of heavy, deep, aggressive riffs combined beautifully with gentle and soft melodies so intrinsic to Nightwish. It is both a typical Nightwish album and at the same time very original. I would disagree with people who say it is not heavy enough - it is just the right amount of heaviness that Nightwish have been putting out there for years. 'Endlessness' is magnificent doom similar to 'Rest Calm', and 'Tribal' and 'Pan' are quite aggressive. Apart from 'Harvest' which I just cannot get into and I think it's the weakest song among the 9, all other songs are masterfully done.
All this being said, the second disc (which contains one long track divided into 8 pieces) might be an issue for many people. I generally like it, with 'Ad astra' being my favourite but it is an entirely symphonic classical peace with no rock or metal. I believe this is why some people have been disappointed by the 'lack of metal' in the album. All 8 pieces require an appreciation for classical music, I personally was not that blown away by them but they are beautiful, just not necessarily my cup of tea. This second disc is an acquired taste. For me as a whole, the album deserves very high rating. Much better, stronger, heavier and memorable than its predecessor. Thank you Nightwish!