Kudos are in order. Oldtimer. Well done, and I hope you can sell many, many copies of your textbooks.

About myself, I'm teaching at a public senior middle school of northern China. Regarding the prescribed English textbook for grade 1 senior middle school students of English that I taught last semester, I've some things to say that will likely interest you. I taught parts of book 2 last semester. It was written by Chinese and Westerners, and was accompanied by audio cassette tapes for listening practice.
On one of the tapes, a native speaker with the accent of an Englishman enunciated 'module three' stressing the second syllable of the word 'module', incorrect pronunciation indeed!
In the book, one of the modules is headed 'Unexplained Mysteries of the Natural World'. But aren't all mysteries 'unexplained'? Else they wouldn't be mysteries, would they? That renders 'unexplained' redundant.
And in a passage of another module, something was mentioned about 'historical relics'. But all relics are historical, aren't they? By contrast, 'relics of historical interest' would have been correct.
Another thing I came across that is bad writing is as follows - usually the module heading did not reflect accurately the content that ensued. Right now, I can't remember an actual example of this, but I do remember a few years ago teaching an earlier edition of the same textbook. in which there was a module headed 'The Silver Screen', which is generally accepted to mean the Hollywood movie industry. But the module went on to talk about the Chinese movie industry, and then about plays, operas and popular music concerts!
No wonder most of the Chinese are so good at Chinglish, they aren't even studying correct English in the first place! The examples above illustrate the very average English levels of the native speakers of English who were hired to participate in the authorship of that senior middle school textbook. But they'll have made a lot of money because the use of the textbook is mandatory in state senior middle schools throughout the country. Mandatory crap, eh! Moreover, I'd be willing to bet that the 'Western experts in English', sic, involved in the writing of the textbook all have CELTA qualifications, and batchelor's degrees in concocting tasty tomato soup....LOL!