The names 'The Star Trek that never was' and 'The Joy Machine' aren't it.
I remember an introduction to the book explaining the authors' credentials' related to the original series as validation for the authenticity.
'Star Trek II: The Lost Series' sounds closer to the title, but I don't remember for sure, but the authors don't sound familiar and it doesn't sound Season 4 related.
Also looking it up, it has more info on production and fewer scripts (2) than I remember.
But some things about it do seem right - the cover looks vagely familiar. The name does sound familiar, though it clearly refers to the new series.
I'm wondering if I'm misremembering some things and that's the right book. Thanks for the tips, let me if any other books sound like the one I remember.
Edit: as I think about it, I think that is the correct book, and I'm misremembering some comments in the book about a fourth season with the 'new series'.
I'm a bit confused about why I think I remember several episodes' stories, and not the other things the book reportedly has, but I think this is it.
Thanks for the help.