One can't take his conclusions seriously, but you can find occasional factoids in his chrono that aren't documented anywhere else.
There's no question that James' knowledge of Trek lore was exhaustive. I'm a fan from 1967, and like James, I read everything I could get my hands on. I had read or at least vaguely remembered most of the sources James so obsessively cataloged.
It wasn't "Treknical" inaccuracy that was his problem. It was that he was a complete frak-head that couldn't get along with anyone.