Some albums that cover other genres with classical instruments end up being very gimmicky. Apocalyptica, however, obviously loves Metallica's music and does an excellent job of arranging it for a cello quartet without losing the original mood of the songs. This album sounds more acoustic than their subsequent, and equally-good, Inquisition Symphony, which gets more electronic and heavier.
Occasionally, the voice part gets a little repetitive since there are no lyrics to provide variation between identical passages, but overall it's a very satisfying album. It should appeal to both metal lovers who are interested in a different take on Metallica and to classical lovers who like their music heavy. Cellists (like me) may find a new appreciation of the capabilities of their cello.