Jenny is ""Swedish Nightingale"" Jenny Lind; Barnum is P. T. Barnum, of course. And the second half of this modestly entertaining novel is devoted to an unexciting, efficiently soap-operatic treatment of their brief, passionate, May/September romance while Jenny was touring America for Barnum just before the Civil War. But Thorp (The Detective, Westfield) seems to have started this book with something more interesting in mind--because the far better first half, while sketching in the Lind/Barnum life-histories, focuses largely on Barnum's prize attraction, business partner, and quasi-son: the smallest man in the world, Tom Thumb, nÃ‰ Charlie Stratton. It is Tom who, while on an 1860 European tour with the Barnum troupe, carries P.T.'s offer to 29-year-old Jenny in Vienna; his first, aghast impression is that of ""a plain, almost frumpy, washed-out, anxious old maid probably too terrified of living ever to change her situation."" And though Tom's attitude will shift--he sees Jenny's beauty, learns of her many admirers (""The audacious flirt, the troubled spinster, and the woman of Christian charity were one and the same""), and shares a moment of drunken near-passion with her on the Atlantic crossing--his primary romantic obsession is with lover Lavinia, a foul-mouthed midget who cheats on him with an alcoholic dwarf. Is Thorpe out to explore the grotesquerie of love, then? So it seems--with lust and jealousy among the midgets, the quest for a mate for pathetic giantess Anna, and inklings of a Tom/Jenny relationship. But once Jenny lands in New York and meets Barnum, this dark, subtly provocative tone mostly disappears as Thorpe concentrates on dramatizing Barnum's PR brilliance (""Lindomania"" is sweeping America even before Jenny arrives), the power of Jenny's austere artistry, and their stormy relationship: they argue about money, about Barnum's freak-shows (Jenny is revolted); virginal Jenny surrenders to him, even though he's fat, balding, married, and ""the villain of her life""; fun-loving Barnum feels guilty; and when the wounded Mrs. Barnum confronts Jenny, the lovers part, drifting into other marriages. The final message? That ""he had taught her the underlying importance of being happy""--a disappointingly pallid windup to a book that begins so promisingly. Still, except for some mushy dialogue, Thorpe writes it all with vivid, atmospheric clarity--and readers partial to historical romance will find this a steadily engaging if ultimately unsatisfying evocation.