There’s danger, hardship, obstacles to overcome, distance to be traveled, and unknown action at every turn—The Call of the Wild is definitely an adventure.
But it's also classified as Children's Literature: which, whoa. Kids used to be much tougher. Instead of, say, a young ginger girl learning about love on Prince Edward Island (Anne of Green Gables) or a couple of small animals having adventures in Model-T Fords (The Wind In The Willows), The Call of the Wild is about a wild beast straining to break free from the stifling bonds of domesticity.
Hmm: now that we think about it, that's a perfect theme for a children's book—provided that those children are approaching puberty (keep the gory dog fights away from the toddlers). In fact, Buck's struggle to join his wolf pack is startlingly similar to the plight of an eleven-year-old who really wants to see a PG-13 movie.