ByJane Stewart Spitzer, Jane Stewart Spitzer reviews popular fiction for the Monitor. LEON Uris's novels ''Exodus'' and ''Trinity'' moved me, captivated me, and kept me up late at night. I expected his latest, ''The Haj,'' to have the same effect, and I was very disappointed that it didn't. The story failed to capture my interest until I was almost halfway through it , and I never got fully caught up in it. The writing is surprisingly poor; many of the characters never come to life; and Uris continually hits the reader over the head with his prejudices against the Arab world and Islam. ''The Haj'' refers to both the pilgrimage to Mecca, a central event in the life of a Muslim, and to the novel's main character, Ibrahim al Soukori al Wahhabi, who, as custom allows, takes the name Haj Ibrahim after his own pilgrimage. The novel tells the story of Ibrahim as seen mainly through the eyes of his favorite son, Ishmael. It is set against Palestine's tumultuous history from 1922, when Ibrahim succeeds his father as Muktar (head man) of the Palestinian village of Tabah, through 1956, when Ibrahim dies in a Palestinian refugee camp on the Jordanian-occupied West Bank. The opening chapters are confused, because Uris jumps around in time and switches viewpoints continually. Granted, in order for a reader to understand the historical events in which the characters are involved, he or she must know something of the history of Palestine. But Uris provides so much information I sometimes wondered if I was reading a novel or a history book - and then how much of the apparent history was really accurate and how much was fiction. Uris paints a richly detailed portrait of Arab life and culture. However, this portrait is also completely unsympathetic to the Arab world in general and particularly to the Palestinian Arabs. In fact, ''The Haj'' reads like a treatise on the evils of Islam and the brutality of Arab culture. It conveys the distinct impression that there is no possibility for a peaceful solution in the Mideast. This pessimism, combined with Uris's prejudices, saps the novel of its vitality and appeal. True, Uris displayed his views clearly in ''Exodus'' and in ''Trinity.'' Yet, because of his sympathy for his subjects, these novels displayed more enthusiasm than bias, which contributed greatly to their readability. This is missing in the new novel. ''The Haj'' also suffers from too little plot and too much talk - most of it in a stilted, awkward style that reads like a translation. It would seem that Uris attempted to capture the colorful, formal style of Arab rhetoric, but the result is unwieldy and boring. Witness two passages from Ishmael's narration: ''the stink was deafening'' and ''we plunged into a spell of nostalgia.'' There are also problems with characterization. The main Jewish character, Gideon Asch, is described in such godlike terms that he never seems real. Ishmael is likable but mainly an observer. His sister, Nada, who is also likable , becomes an important character only toward the end of the book. And Haj Ibrahim, who is partly appealing, loses the sympathy of his son Ishmael - and the reader - when he kills one of his daughters for breaking the sexual taboos of Islam. It is obvious that Leon Uris spent a great deal of time and thought in researching and writing ''The Haj.'' Running to almost 600 pages, it demands a major commitment of time and thought from the reader as well. It is unfortunate for both author and reader that ''The Haj'' isn't a better book.