It is excellent for the DIY'r. I regularly attended RR factory tech meets conducted by Cal at their NA headquarters in Lyndhurst, NJ. The RROC store may be bringing it back. His widow controls the rights.
I heard the copies have been sold out for sometime but that RROC is working on a plan to republish it.
I will try to verify that next week at the annual gathering. Sounds like what Wraithman said is the scenario indeed.