the topic of soviet policy towards Vietnam is not a heavily researched one and the majority of what exists is heavily tainted by American views and a reliance on propaganda laced official statements of the Soviet government at the time. Gaiduk was one of few who was able to look at the Soviet declassified archives during the short time that they were open and thus his book is built on information which was never released and which better represents the motives and characteristics of the Soviet (and also Chinese to some extent) foriegn policy towards the Vietnam War. Very intersting if the subject interests you. and an integral perspective which can be found few other places.