I'm reading the .epub-format on my
PC using the Adobe Digital Editions software. Works like a charm. I don't really think they are worth as much money as Black Library wants to have for them, though. Pretty much a collector's item, I suppose, but almost a full third of the file is "packaging" such as the cover, the credits section and advertisements, and half of the rest is fancy pictures. Obviously, this problem may be less severe with the bigger/longer files, though.
If you have the coins to spare, take a look and just order one of the cheap ones to see for yourself. At least it's not much of a loss even if you don't like what you got.