Basic descriptions of DT-albums:
1. Skydancer (1993): The band's debut with 9 rather long, epic songs in the best Swedish melodic death metal tradition. Complex song-structures with multiple tempo-changes and very little repetition. A good balance between brutality and melodic beauty - the latter occasionally based on acoustic guitars and clean singing (both male and female). The weak points of the album are the thin production and relatively poor vocals (by Anders Friden, later the vocalist of In Flames). Also, it isn't an album that opens up on the first listen, so you better have some spare time when you buy it. It is nowadays available with the songs from the "Of Chaos and Eternal Night" MCD (1995) as a bonus on the same CD - the 3 new songs from OCaEN are more in the style of their following album, The Gallery, plus there's a remake of the last Skydancer-song with new vocals.
2. The Gallery (1995): The breakthrough-album that raised the band from the underground to the forefront of the metal-elite. Still hailed by many as the band's best album, a true classic of the "Gothenburg-style". The same elements that were already present on Skydancer are here (although the male clean vocals are almost nonexistent), but no more are the subtle nyances shrouded amidst the complex compositions - now everything is at the forefront, thanks for the major part to the improved production. Guitar-driven technical melodic death-metal, with lots of hooks in all the songs. My personal favorite, but it has to be said that some people find this one too "easy" and not deep enough for repeated listenings.
3. The Mind's I (1997): A step towards even more compact song-writing and shorter, thrashier songs. Possibly the most brutal of all DT-albums. Has a rather uneven mixture of songs, ranging from the lighting-fast opener to the soothing closing-track. Might not be so easy to get to, but a classic in it's own right, nevertheless. The MCD "Enter Suicidal Angels" (1996) has one song from the album, plus three extra-songs, one of which is a crappy techno-remix.
4. Projector (1999): The most controversial album from the band. A slower, more melancholic album with some gothic touches here and there. Divided the band's fanbase clearly in half back when it was released with its abundant usage of clean vocals (mainly male; female only on one song) and less complex songwriting. A firm favorite of many fans both old and new, but certainly not representing the same style as on the other albums. Overall quite a unique combination of various styles, (death) metal being only one of them.
5. Haven (2000): The first album of the modern DT-style. The addition of electronics brought a fresh aspect to the band's sound, while retaining the old basics of combined aggression and beauty. A tastefully made step to a new frontier, but considered by some to be less enduring than the other DT-releases. The cathcy riffs and keyboard-melodies make the album very easy to get into, however.
6. Damage Done (2002): The latest new album by the band, partly a return to the roots, partly a careful step forward. Combining the brutality of The Mind's I with the electronic sound of Haven and with the emphasis on guitars of The Gallery, the album pretty much sums up those aspects from the band's repertoire. A very solid album with 12 strong songs, but not quite yet the bold leap to new dimensions some fans were waiting for - the next album, perhaps...
In addition to these, the recent double-CD by the name Exposures - In Retrospect and Denial (2004) collects the band's pre-Skydancer demos and rare bonus-tracks in one package with the audio-part of the band's live DVD Live Damage (2003). Although I like Exposures very much, I really think it is made more to us old fans than to the newcomers. Thus, I recommend you get the other albums first.
Hopefully this was of any help - the opinions expressed above are probably quite subjective, so beware. And sorry for the brevity, but I got to go to the sauna now.
-Villain