One of our favorite writers, Thubron captures in dazzling prose the contradictions, beauty, personality and hardship of this huge land. Thubron journeyed 15,000 miles along the Trans-Siberian Railway, up the Yenisei River to the Arctic, into the mountains abutting Mongolia, to Lake Baikal -- the world's oldest and deepest lake -- and east to Magadan and the Pacific.  (SIB14, $14.95)