The Irish playwright Leonard (the Tony-winning Da; two memoirs, Home Before Night and Out After Dark) turns to fiction with a witty, glitteringly dramatic treatment of the by-now mythic love affair of Charles Stewart Parnell (1846-91), the Irish leader who fired the drive for Home Rule, and English-born Kitty O'Shea. The affair eventually ended Parnell's leadership and shattered the unity of the Irish party in Parliament. Kitty O'Shea married handsome Willie--the vain, weak, and shifty son of a Dublin solicitor who had edged into Parliament from County Clare--through a regrettable impulse, and now, at 35, she feels ``hardly used'' by life. The meeting with tall, gaunt, ailing Parnell (the lion she had not yet netted for a dinner party) is as brief as the swing of a sluice gate--the two adamantine egos are well matched. Leonard's Parnell, who, growled the Irish Secretary, ``cold-bloodedly incited the Irish to peace,'' detests the noisy adoration of ``dear old Ireland'' and has the aristocratic pride of Lucifer ``who chose to fall sooner than serve.'' Kitty, who insists that Parnell carry the generally detested Willie on his coattails because she needs a husband of status, declares, ``Not because I care for him. I care for myself!'' Meanwhile, whether in cool amusement or cold fury, Parnell, the brilliant political tactician, collects thorny victories--and enemies, principally among his most devoted lieutenants. No slouch at tactics herself, Kitty at one point skewers Willie, who finally learns that two of their children are Parnell's, and loses a legacy. There are runnels of scandal, divorce, marriage, and the Irish party ``takes its own life.'' First-class portraiture--from the Grand Old Spider Gladstone to Tim Healy, a ``lover betrayed,'' and, of course, the lovers themselves, brilliantly realized, who labor on through mighty times.