Immortal is awesome...Now for my lengthy reply...If it's Sons you like, the two previous albums, Damned In Black, and At the Heart of Winter is what you should buy. The earlier albums are much more raw in sound (much more true), but ATHOW and DIB are more like the evolved Immortal you hear on Sons of Northern Darkness. ATHOW is like the melodic side of SOND, while DIB is more aggressive. Both excellent albums. Stick to those 2 albums if you have any aversion to true black metal production. If you have no problem with bad production, get all of Immortals recordings. IMO every one of them is essential. Some earlier recordings have Demonaz of guitars, but you'd love him just as much, the riffs are breathtaking, the vocals are spectacular, always have been. And buy Battles in the North, as that seems to be common consensus.