Chains is full of really solid uses of figurative language.  Isabel might not be that formally educated of a girl, but her story telling language skills are very good.  Throughout the book, Isabel makes large usage of similes.  One of my favorite similes in the book is when Isabel describes what somebody's wig looks like.  

Looked more like a dead possum than a wig. 

Similar to a simile is a metaphor.  A metaphor makes a similar comparison between two different things, but a metaphor won't use the words "like" or "as" to make the comparison.  Isabel uses a great metaphor to describe herself while she is closely listening in to Master Lockton's Loyalist plans.  

I am a bookcase, I am a piece of furniture.

Isabel is willing herself to be as unnoticeable as a piece of furniture.  That way she can hear the full details of the plan.  

Another type of figurative language is hyperbole.  Hyperbole is exaggeration for the sake of emphasis.  I like the following example from Chains.  

I feared my ears might drop off.

I'm quite certain that a person's ears are not capable of just falling off, but it effectively sells the point.