It doesn't seem to have have transcripts of the "discussions the Japanese war cabinet had behind the scenes", which is specifically what you wanted people to look at in your former comment.

Transcriptions are not available, obviously, but the closest thing I've seen to date is "The Day Man Lost: Hiroshima, 6 August 1945", which is available in English. Compiled by the Pacific War Research Society, a group of Japanese historians, from accounts from officials and written records, their version of history does indeed claim that the Japanese government was pinning their hopes on the Soviet Union brokering a peace agreement with the United States and was deliberately delaying responses to the US until their hopes were dashed by the Soviet declaration of war. The use of atomic weapons was an additional impetus, not a deciding factor.

As an aside, the book makes for fascinating reading. Being compiled by Japanese from accounts by other Japanese, one has to be wary of a certain amount of face-saving and retconning, of course. However, it's the first I've seen that overlays the timeline of events occurring within the Japanese government with the US progress in the war.