Switching from mystery/intrigue to straightforward character novel, author Smith ( Gorky Park ) roughly outlines the development, under J. Robert Op penheimer, of the first nuclear weapon at Los Alamos, New Mexico. The im pending test blastwith its foregone historical conclusionserves as little more, however, than anchor and chro nological end frame to an otherwise aimless plot exhibiting muted prose, wistful philosophy, and nonexistent suspense. In central focus, yet not fully realized as character, stands Sergeant Joe Pena, an independent Pueblo Indi an and self-contained veteran of mili tary action (mostly as boxer and pia nist) in the Philippines who drives for ``Oppy. '' Joe's episodic antics (he likes to flout authority) juxtapose natural (i.e., Indian, the desert) and unnatural (i.e., U.S. Army, the bomb). Evocative at times, but largely unsympathetic and ultimately inadequate. BOMC alter nate. Rex E. Klett, Anson Cty. Lib., Wadesboro, N.C.