Both are grasping at a simplicity they don't find when they look carefully.
So, things like Jaynes posits might have happened, but you cannot get support for it from neuroanatomy.
To clarify, popularized over-simplified descriptions of the left hemisphere being "analytical" and the right hemisphere being "creative" are inaccurate, but left/right hemisphere differences do exist and appear to exhibit consistently different approaches to things. The book 'The Master and His Emissary' covers the more recent research in that area, and is at least as interesting of a read as 'The Bicameral Mind' was.
https://www.tandfonline.com/doi/full/10.1080/13546805.2010.5...
https://ajp.psychiatryonline.org/doi/10.1176/appi.ajp.2011.1...
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2828853/
https://link.springer.com/article/10.1007/s11097-011-9235-x
> it is worth noting that the book has been much praised by neuro-scientists as diverse as Ramachandran, Panksepp, Hellige, Kesselring, Schore, Bynum, Zeman, Feinberg, Trimble and Lishman.
It'd be surprising if it were poorly received regardless, because the book itself is little more than a review of the relevant literature on the topic, packed with references, and some added philosophy about it's implications sprinkled on top. Not that much different from one of Michael Gazzaniga's popular books, and certainly not as out there as Julian Jaynes.