Blackwater Park is the one that got me into Opeth. But I still don't think it's as good as Morningrise or My Arms Your Hearse. And Morningrise is probably the most accessible, of those two. So get that. Of course, there is no BAD Opeth album, they're all amazing. I wouldn't recommend getting Damnation first though.
Opeth- start with Blackwater Park or Still Life. They are the best place to start with the band. Morningrise and Orchid are quite tough to get into at first, and you might as well stay away from their more aggressive side (My Arms, Your Hearse and Deliverance) until you are used to their more varied styles.
i think that Still life is a very good Cd to introduce with Opeth because it is very melodic and hard at the same time (like opeth it is). but them you should check all the albums because they are excelent. you should think that each album is recorded in diferent years so the mature was increasing while the time was pasing.
with Death Symbolic is the top of the mature. this is very original album with lots of melodies and hard and sharp riff. them check it all because death is a clasic and is the group who give a name to a style. Death is incredible.
With Death, I'd recommend starting with Symbolic, its very catchy and not as complex as the best, TSOP.... although it is complex in its own right.... Opeth, definately get Blackwater Park.... it hooked me immediately.... its not just music.... its much more.... AND DON'T LISTEN TO ANYONE WHO SAYS ITS BORING!!!!!! Jesus christ....
I bought The Sound of Perseverance on ebay and did not like it at all. I could not stand the vocals, the drums were really annoying, and the songs went absolutely no where. I admire the band members, they have considerable chops, but the songs simply didn't grab me even after numerous listens. At least with older Opeth, esp. Orchid, the songs had some flow to them. Here, it all seemed random and unorganize. I would like to get Human sometime, because it has a couple of the guys from Cynic on it, and Focus is an absolute masterpiece.