Worst nonfiction book that I have ever read for accuracy was 'The Mother Tongue - English and how it got that way' by Bill Bryson. The guy is a journalist and only speaks English, and the stuff he put in his oeuvre where he compares English with other languages or talks about imported words seems to have been made up of factoids gathered from newspaper and magazine clippings, plus the occasional input of mischievous foreign waiters who knew he'd stiff them on tips and lied to him with smiles on their faces.
Amongst his claims:
- Finnish has no swearwords, so the Finnish say 'ravintolassa' (in the restaurant) instead
- he perpetuates the Eskimo vocabulary hoax about how many words for snow they have
- 'bumfodden' is not a German word for toilet paper
- According to him, 'The French for instance, cannot distinguish between house and home, between mind and brain, between man and gentleman', which must be news to the French (and certainly is to one Amazon reviewer)
- English is superior because other languages don't have thesauruses
-The existence of the word 'schadenfreude' is indicative of German sensibilities. Huh, German has no word for 'bully' - is that supposed to say anything about all those millions and millions of native English speakers?
-Esperanto has no definite article - yes it does
This goes on and on. I speak and read four languages to varying degrees and have studied and mostly forgotten two more, and he talks nonsense about every one of them. Reading the Amazon reviews is quite amusing, if a bit disheartening. The reviewers who speak any foreign languages or have a bit more insight into English linguistics think it is atrocious. Everyone else thinks it's wonderful because it's so funny, never mind the facts. There's even a teacher who says she'd still use it in her lessons because it got her kids so enthused. A book with an error on every page.