I think pacing and atmosphere are relative in terms of the characters and intrigue that's originally set up.
If the book really starts dragging, but i am completely invested in a character- I will still follow it through to the end (although I might peek; oh the shame!) <img src="/images/graemlins/blush.gif" alt="" />
Atmosphere; I think that more or less depends on your own imagination. I read authors like Tom Clancy and think "Get on with it! I don't have to be told what every single bolt in the sub looked like." Sometimes being given so much information is like being spoonfed, its annoying. IMHO