You can't lump too many people into the same sphere with London...Twain, Poe, and Lovecraft are a few that spring to mind. He's an American Titan, and he gets the fawning treatment you'd expect from the Library of America in this exemplary, extraordinary, green-registered book.
Call of the Wild is a page-turning yarn about a dog that becomes a wolf. It's listed on the MLA 100, but any competent kid of ten could tackle it...and enjoy it.
White Fang is a canine bildungsroman that inverts the plot of Call of the Wild, with the wolf becoming a dog. Also a page-turner, also something a kid would read without having to be coerced, and possessed of a truly classic scene where White Fang fights a bulldog.
The Klondike Short Stories are all superb--some people think London's metier was the short story rather than the novel--with Batard being a personal favorite.
The Sea-Wolf is a work of genius...until it all comes crashing down with the introduction of Maud Brewster, and the escape to Endeavour Island. What had heretofore been a truly transcendent work of art transmogrifies into a clunky, melodramatic, and tedious chore, where London's love of sailing jargon threatens to overwhelm the reader.
The Selected Short Stories show that London wasn't just a Yukon guy...he had some other arrows in his quiver. A few stories demonstrate his--at the time--devout socialism, which lasted up until he himself got rich. The Apostate is the weakest of these, but The Strength of the Strong is a pretty good allegory for fin-de-siecle capitalism, with all its gory excesses. London also writes convincingly about such diverse topics as boxing, South Sea cannibals, and straight-up science fiction.
This book of books is excellent, and any American who fancies himself a lover of literature would be remiss in not reading it.