That is a difficult question: I only have two Sol Invictus albums myself. Broadly speaking, the trajectory goes from quite primitive 'industrial folk' in the early material to a more ornamental style with professional violins and cod-classical arrangements later on. So it depends on whether you prefer 'rough' or 'smooth'. Either way, Tony Wakeford's singing stays the same throughout his career: monotonous and often tuneless, but strangely mournful and captivating nonetheless.
The early 1990s albums 'Lex Talionis', 'Trees In Winter' and 'The Killing Tide' are representative of the early style (I own the first of these). I'm not sure how variable the other two are, but any of them would probably be a good place to start. There is also the compilation 'Sol Veritas Lux', which combines early studio and live recordings. Ian Read - who went on to form Fire + Ice - shared the vocal duties on the first few albums.
'King & Queen' apparently introduced the more elaborate instrumental style, and this was developed on 'In The Rain' (1995), the second album I own. 'In The Rain' has a lush string background throughout: in my opinion the success varies, since Wakeford's flat voice sometimes seems to conflict with the backing, although most fans enjoy it for this reason. Also, for enthusiasts of real classical music, the arrangements can sound trite in a Hollywood soundtrack way, depending on your mood.
I have not heard any of the later period material: 1997's 'The Blade' was supposedly a return to old form, but since then he has introduced 'jazzy' elements, which obviously one will either love or loathe (I'm afraid I fall into the latter category, running a mile from the term 'fusion'). You probably need a response from a bigger Sol Invictus fan, but I would certainly recommend something pre-1995 to start off with before you investigate the later stuff.
Edited by: indarknessletmedwell at: 4/8/04 4:46 pm