The BAM splits from Trans-Siberian Railway at Taishet, some 700 km. west of Baikal lake, and passes the Baikal from the north at Severobaikalsk. It then goes parallel to the Trans-Siberian Railway all the way to the Pacific Ocean. You can expect great landscapes, admirable views of Baikal lake and a lot of high bridges and tunnels.
The railway was built primarily for military reasons as a backup to the Trans-Siberian, which runs quite close to the Chinese border. The first stage, from 1930 to 1953, was built largely by Gulag prisoners, including German and Japanese prisoners of war, and an estimated 150,000 people died in the process. Work halted due to Stalin's death, but started again in 1974 as a Komsomol project, this time "with clean hands only" (in Brezhnev's words). The line was officially completed in 1984, although actual work continued until 1991.
The BAM terminates at Sovetskaya Gavan on the Pacific Ocean, but most visitors opt to stop at Komsomolsk and head from there to Khabarovsk in order to rejoin the Trans-Siberian to Vladivostok.
For most of its length the BAM is single track. It is also not fully electrified. BAM was a huge Soviet project, and workers from all parts of the Soviet Union were brought to construct it. While traveling on the train pay attention to station buildings. Often they symbolize (in their architecture) the region from where the building crew came. Many of these workers married and stayed there, so you can find settlers from distant parts of the former Soviet Union along the line.
A number of years ago, there were rumors about construction of a second track and another wave of workers came seeking work and remained. Construction didn't start.
Sometimes trains stop at turnouts in remote locations to let trains from the other direction pass. There are a few passenger trains going from Moscow all the way to the Pacific; however, there are many local trains, with the main "traffic" being wood transports from the Siberian forests.