Personally I like the voiced version, because it saves me from reading the lines ^ ^ and also it kind of enhances the emotion because you can actually hear the emotions portrayed by the VAs.
The silent one is also quite powerful because of the 'death-burding' feeling when you reading it.
I suggest reading unvoiced first then go back to voiced version
There are a few more good novel games out there, like planetarium (sp?) or a lot Leaf's work are all good starting points. Some of these novels will take you more than 8 hrs to read, but with music as enhancement you often loose time and want to finish the story.
Unfortuantly no English company are willing to take up translation these novels because it takes too long and not worth it.
I highly recommend if you have nothing to do, give Narcissu a go
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