Rammstein has my vote as one of the three best metal bands ever. With this, their fifth album, they continue their mastery of the genre. This mix of fast and slow is always dark, although some songs deceive if you don't understand German. For example, Feuer und Wasser is explicit and voyeuristic and tender and eventually sad and angry at once. Rosenrot is a sly take from the classic Goethe poem Roeslein auf der Heiden, but blames the maiden, not the boy. Te Quiero Puta is sung in idiomatic Spanish with a saucy Spanish rhythm and a saucy Spanish female voice. Benzin reminds me of Metallica's Give Me Fuel, Give Me Fire, and is a hard driving song with inflammatory lyrics. Wo bist Du is another great mix of rock and lyricism.
Favourite Rammstein? It's really hard to choose. They all rock hard, they all have deep roots in German and other European literature, they all echo musical ideas from ages past, and they're all original. Probably a tie between Rosenrot and Reise Reise, with a nod to Mutter.
I think you should get them all.