Written, But Read?

The latest book for the neighborhood book club, The Philosophical Breakfast Club, gives the impression that the author did not bother to read over manuscript or proofs before publication. I find in the second paragraph of Chapter 11, "New Worlds"

[Neptune] was only the second planet ever discovered...

Yes, I know what she means. And in

elegiacs, a classical form of funereal verse famously employed by Ovid in the seventh century BCE

(second-last paragraph, same chapter) I can see where the mis-assembled bits come from. But should I be stopped to puzzle over that or its like?

Were Ovid the only such slip, I'd write it off as a simple lapse. But passing items in the book lead one to wonder whether the author knows customs from excise; remembers the Jane Austen she cites; knows what Kant was getting at; can distinguish the tendencies of French Revolution of 1789 and on from those of 1848; has considered the implications of Deism.

The author also stretches inference. In one paragraph of Chapter 10, "Angels and Fairies", I find "may have made a suggestion", "had not apparently occurred to him", and "perhaps the idea had not been compelling.", all this to explain why William Whewell proposed marriage to Cordelia Marshall in 1841 rather than at their first meeting in 1838 or so. The second paragraph following begins "Once the idea was put to him, ..." Was it?