Great series:) Lets see how the order works... *digs through a stack of paperbacks*
"The Black Company", "Shadows Linger", and "The White Rose" are all a connected, straightforward narrative, the Books of the North.
"Shadow Games", "Dreams of Steel", "Bleak Seasons", "She is the Darkness", "Water Sleeps", and "Soldiers Live" are the books of the South.
"Silver Spike" takes place directly after the books of the North, parallel to "Shadow Games". Either one can be read first, because they both make some references to the other, which wont fully make sense until you read the other. Does that make sense?
Anyway, I read Shadow Games first, then Silver Spike, then continued the books of the South. A friend of mine read Silver Spike first, then Shadow Games. He claims that it made perfect sense, but now sometimes he'll laugh at the wrong things.