has a problem with the artificial plot twists and tidy resolutions of popular novels

UPDATE: As shown here, all the key terms in the Captain's trenchant critique of G. P. R. James are (surprise!) well exampled Melville's known writings.

In January 1852, a "Captain of U. S. Dragoons" criticizes The False Heir by G. P. R. James, then Herman Melville's Berkshire neighbor:

The hero is a lad of seventeen; old enough to fall in love, and but little else. St. Medard is a mere abstraction, De Langy a cipher, Artonne a riddle, Monsieur L. a man in a mask who puts himself in the way sufficiently to give some interesting trouble and help out the plot. In the most commonplace manner, he has thrown the hero and favorite characters into difficulties for the transparent object of a final triumph; he disinherits the hero, shipwrecks his best friend, St. Medard; confines Artonne in prison for murder, and last, not least, sends his best-drawn character, Marois, to the galleys!"

Scenes Beyond the Western Border, Southern Literary Messenger 18 (January 1852): 49; and Scenes and Adventures in the Army.

In Pierre (1852), Melville likewise faults popular novels for too-tidy conclusions:

Like all youths, Pierre had conned his novel-lessons; had read more novels than most persons of his years; but their false, inverted attempts at systematizing eternally unsystemizable elements; their audacious, intermeddling impotency, in trying to unravel, and spread out, and classify, the more thin than gossamer threads which make up the complex web of life; these things over Pierre had no power now. Straight through their helpless miserableness he pierced; the one sensational truth in him, transfixed like beetles all the speculative lies in them. He saw that human life doth truly come from that, which all men are agreed to call by the name of God; and that it partakes of the unravelable inscrutableness of God. By infallible presentiment he saw, that not always doth life's beginning gloom conclude in gladness; that wedding-bells peal not ever in the last scene of life's fifth act; that while the countless tribes of common novels laboriously spin vails of mystery, only to complacently clear them up at last; and while the countless tribe of common dramas do but repeat the same; yet the profounder emanations of the human mind, intended to illustrate all that can be humanly known of human life; these never unravel their own intricacies, and have no proper endings; but in imperfect, unanticipated, and disappointing sequels (as mutilated stumps), hurry to abrupt intermergings with the eternal tides of time and fate.  --Pierre; Or, The Ambiguities