In this quote from S.E. Hinton's Rumble Fish, "What strange lives you two lead," what language technique is evident?
"Russel-James," he said suddenly. "Are you ill?"
"Got cut in a knife fight," I told him.
"Really?" He came over to take a look. What strange lives you two lead."
The language technique evident in this quotation is a rhetorical device called "hyperbaton." Hyperbaton is the reversal of normal word order in speech or writing. Hyperbaton is an umbrella term for a number of kinds of sub-categories of hyperbaton (word reversals) such as anastrophe and hypallage.
A general hyperbaton inverts the normal word order of a sentence for the purpose of giving dramatic or emotional effect. Since it is a language technique that doesn't need to be taught for it to be used, like chiasmus (criss-cross parallelism) needs to be taught, it may be a spontaneous expression emphasizing a result of something as being more important than the thing.
English Word Order: English word order puts the Subject first, the Verb second and the Object (the "what" and "to whom") third: Subject Verb Object or SVO, for example, "Jana threw the ball to Tanya." An SVO analysis of this word order shows this: Jana (Subject) threw (Verb) the ball (Direct Object) to Tanya (Indirect Object) or "Someone (Jana) did something (threw) with something (the ball) to somebody (Tanya)."
Let's analyze your quote to see where the hyperbaton occurs. "What strange lives you two lead." The Subject is a delayed one: it does not appear at the head of the sentence. The Subject is "you two." The Verb follows that and is "lead." The Object is "strange lives." "What" is an adjective here that expresses an implied comparison between normal and strange lives. It serves the same purpose as the adjective "such," which could substitute for "What" without altering the meaning or emphasis: "Such strange lives you two lead."
If we put the sentence into correct SVO order using "such," we get, "You two live such strange lives." In this construction, the Subject has the emphasis and draws the attention. In the hyperbaton construction, with the relocated adjective modified noun phrase "what strange lives" ("what" functioning as an adjective indicating an implied comparison), the emphasis and attention goes to the strangeness of their lives.
In the quote, "What strange lives you two lead" (taken from Rumble Fish), S.E. Hinton has inverted (or reversed) the traditional sentence structure. The sentence, in traditional structure, would read as follows: "You two live strange lives."
In the sentence, Rusty-James' father is talking to Rusty-James about a knife fight he (Rusty-James) got cut in. The use of the word "what" would traditionally signal an interrogative sentence (one which asks a question). Here, it is more of a statement.
One last language technique used in the sentence is irony. Given that Rusty-James' father had a strange life of his own (leaving and binge drinking for days on end), calling Rusty-James' life strange is ironic.