Within Temptation's previous album (Mother Earth) was interesting, pastoral themed gothic & folky metal (Like "All About Eve" only with the added metal guitars and keyboards)
It worked well enough but as an album it was a bit uneven.
The Silent Force sees WT really come into their own and embrace the power of the full orchestra. Amazingly, they've pulled it off and the orchestration has brought grandeur without bombast and bold sweeping sounds without the excesses of opera.
It's the best album I've bought this year (and believe me I've bought a few).
Stand My Ground is a great track for hooking in the casual listener and is close enough to songs by Lacuna Coil, Nightwish or even Evanessence to get mainstream attention, but the rest of the album is best listened to as a whole piece.
The bonus tracks A Dangerous Mind and Swan Song on the 'special edition' are both excellent additions and feel very much like part of the album.
Current favourite tracks are Stand My Ground, Angels, It's the Fear and Swan Song, but there really isn't a bad track on the album.
To sum up, if you liked their last album, you should adore this one. If you like Nightwish 'Once', this is similar but in my opinion a better album.
If you like the sound of female fronted metal with a symphonic backdrop, you'll love this and if none of that appeals to you, I'd urge you to give it a chance.