If a picture is indeed worth a thousand words, then this slim album that contains nearly 200 black-and-white photos speaks volumes. The Private World of the Last Tsar, edited by Paul and Beatrice Grabbe (Little, Brown: $25), contains photos such as might be found in any family album--scenes of a family picnic, a teen-age girl standing in a field of daisies, a boy in a sailor suit playing on the beach. Yet, they have a haunting quality, for the peaceful scenes serve as a prelude to disaster for a family--and a way of life--that was out of touch with reality. The family is that of Nicholas II, his German-born wife, their four daughters and their son, Alexis, the frail, hemophiliac heir to the throne of Imperial Russia. All were killed in 1917 by Communist revolutionaries in a cellar in Ekaterinburg, now the Soviet city of Sverdlovsk. The pictures, published for the first time, and a fine text that includes diary excerpts from the photographer, Gen. Count Alexander Grabbe, a military attache to Nicholas and father of Paul Grabbe, offer a dramatic short course on the last years of the last Romanov to rule Russia.