The book accuses Russia of detonating explosives in four apartment buildings in 1999, killing more than 300 people, then blaming Chechen rebels.
The New York Times article claims,
...Litvinenko was not the first former or current Russian official associated with the book to be assassinated. The authors chronicle the slayings of three of their principal sources, all members of parliament. Two were shot dead; the third was poisoned.
Russia has banned the book, only adding to the speculation that there is truth to the book's claim.