That sounds damn interesting, but I was not aware that the Chinese had any SSBNs in 1968. Was this a sub that surfaced to fire horizontally-stored rockets?
You've got the right idea, except for the horizontal storage.
China had received at least one (possibly three? I may need to re-read the book) Golf I type SSBN from the Soviets in the early 1960s, prior to the breakdown of relations between Moscow and Beijing; the Golf I had to surface in order to launch, and carried 3 SLBM's with a range of about 350 NM (although these were vertical-launch tubes, not horizontal). By contrast, the K-129 was a Golf II class, able to launch while submerged and carrying 3 SLBM's with a range of 800 NM -- but otherwise very similar (as in almost identical) to a Golf I.
Ergo, when preparing to lanuch on Honolulu, K-129 took up a firing position about 350 NM northwest of Hawaii and surfaced in order to launch -- thus mimicking the firing profile of a Chinese Golf I.
According to Sewell's research (and a certain amount of ex-submariner's educated conjecture), the persons in control of K-129 had the missile's arming codes and launch codes (the warhead was live and the rocket engine was ignited) but they did not have the correct Fail-Safe codes (which codes the Soviet Fleet Command changed without prior notice from time to time). As a result, the missile's Fail-Safe exploded and sank the entire sub.
And, a few years later, the CIA sent out the Glomar Explorer to investigate the sinking and figure out what happened; and a few years after that, former submariner Ken Sewell pieced together all the data he was able to gather on the subject and wrote a book about it.
As to Sewell's conjectures about the Communist Party faction which had taken control of the sub at time of the launch attempt (hence his description of the sub as a "rogue"), I'll leave you a few spoilers to glean from the book itself.