In July 1898, when he was still in Siberia, Lenin married Nadezhda Krupskaya. In 1899 he wrote a book he called "". In 1900, Lenin was set free from prison and allowed to go back home. He then traveled around Europe. He began to publish a Marxist newspaper called "Iskra", the Russian word for "spark" or "lightning". He also became an important member of the Russian Social Democratic Labour Party, or RSDLP.