Harrison, known primarily for fiction of a feverish, melodramatic kind, makes a surprisingly sober historical novel out of the contrasting, intertwined careers of Nile explorers Sir Richard Burton and John Speke: while emphasizing Speke's supposed psychosexual hangups, the narrative sticks close to the year-by-year facts throughout--which, though conscientious, sometimes results in repetition, a slow pace, and a lack of dramatic shaping. They meet in 1854. Burton is the notorious explorer/rake/anthropologist, mingling with the natives, collecting sexual data first-hand, but steadily, patiently gathering evidence in his search for the source of the Nile. Speke is a colonial snob, a repressed, dyslectic young soldier-aristocrat, at first interested only in hunting. But after an initial, hapless expedition into Somaliland with Burton, Speke catches explorer-fever, of a sort: ""I must have fame""--because ""Speke felt he had to earn the right to be sexual and completely alive."" In 1857, then, Speke joins Burton's great, illness-plagued trek into the interior, as the two men's utter dissimilarity creates increasing friction: Speke is disgusted by Burton's leisurely approach, his native-girl wenching (""a dabbler, a poet, a gregarious scholar who seemed to lack any single-mindedness""); Burton sees Speke as incompetent, impetuous, a fool (""he has a tendency to abuse himself physically instead of getting any job done""). But it is Speke who locates and names Lake Victoria--and, breaking a promise to Burton, he prematurely announces his find to the world. (""I discovered the source of the Nile by myself while he stayed behind with some whores in an Arab slave camp."") So the men are soon bitter enemies back in England: Speke is malicious; Burton is angry but reasonable in his attacks of Speke's valid yet unproved discovery. Speke, now famous enough to become sexual (first with native girls, then with men), sets out to re-explore, to back up his theories with evidence. But, while Speke's basic claims are in fact correct, his un-scientific sloppiness will result in horrid reviews for Journal of the Discovery of the Source of the Nile . . . and suicide. Harrison freely plays plays psycho-biographer here--with Speke's relationships (repressed lusting for Burton himself), the fame/sex interface, the suicide (called an accident by others), and Button's free sexuality (cf. Fawn Brodie), in and out of marriage. Still, most of this is reasonably convincing, never too sensationalized--though the dutiful historical digressions (Burton's US travels, his palship with Swinburne, etc.) often detract from the central personality conflict. And, if the second half thus tends to drag, there's a rich blend of speculative psychology and exotic travelogue in the first--as Harrison provocatively pits a liberated, humane explorer (the pro-Burton bias is marked) against a neurotic, fame-seeking opportunist. Sprawling, intermittently fascinating bio-fiction overall--seriously limited as exploration drama, however, by the absence of any maps whatsoever.