If you could use a sledgehammer as delicately as a scalpel, you might have some idea of how London writes. He doesn't go in for flowery language, complicated metaphors, or ten dollar words. "White Fang became a fiend" (17.1) is pretty hard to misinterpret, and gets the point across quickly.
His straightforwardness helps move the story along, as well as keep the action front and center. But because he chooses his words so carefully, he's able to pack a powerful punch into each one. White Fang feels like a much more descriptive book than it is, thanks to swift, deadly sentences that strike without warning and leave a powerful impression behind.
The incredible thing is that, while London may skimping the details, he also packs a heck of a punch into the words that he does use. He makes a lot of suggestions and asks us to infer quite a bit, which lets our minds fill in the blanks that his rough-and-ready dialogue leaves.
For example, check out the first time White Fang encounters the Native American gathering, when he "came upon it suddenly." (9.1). "Suddenly" says a whole lot: it's exciting, it's tense, it's a little surprising. And yet he still hasn't told us what "it" is. The word increases our apprehension and suspense, and adds a whole lot to the atmosphere of the gathering (as well as White Fang stumbling into it). All that with one little word. And hey, why use six words when one word will do?