If you like TDH, go for "The Light at the end of the world", it is the one previous to TDH, and is pretty similar. After that, "The Angel & the Dark River is probably the next one to get (no death vocals on this), then "Like Gods of the Sun" (assuming you want to keep buying their albums
). After that, if you want some all-death vocal stuff, give "As the flower withers" or "Trinity" a shot, or for a more 'modern' approach (again, all-clean vocals), "34.788% complete".
In regards to 34.788%, I hated it initially, but now really like it. It is a little different from their other stuff, like I mentioned before, more of a 'modern' feel to it. It kinda lacks the over-the-top dramatics of other albums, the songs are more direct and to the point. And there is a trip-hop song, which most people hate, and everyone that hates the album seems to have based their opinion solely on that song, rather than all the others (it's a rather boring song too, but there are 6 others to get into). The opening track, "The Whore, the Cook, and the Mother" is one of their best, and quite stunning.