Book briefing: varied smorgasbord from independent publishers; Cocktails at Somoza's, by Richard Elman. Cambridge, Mass.: Apple-wood Books (Box 2870, 02139). $10.95.

Elman first went to Nicaragua in 1978 at one of the critical moments in the Sandinista guerrilla struggle against the Somoza dictatorship; he returned in September 1979 after the Sandinistas had triumphed. These trips are the grist for his very readable though inconclusive "Cocktails at Somoza's," a title drawn from one of the many parties that the late dictator hosted for the foreign press.

Most of the book, however, centers, as it should, on the Sandanista phenomenon. Elman spent much of his time with the guerrillas before they became governors, getting to know many of them quite well. In many ways, what has happened since they became Nicaragua's leaders is the more important story, and, though some readers may object to some graphic accounts of brutality or oc casionally tasteless language, Mr. Elman tells it well.