The book is only releasing on 4 February and even later in some places. The buzz around it is from de Changy's pre-release publicity campaign, that I believe will only get more intense in the next few days. IIRC her last book, in French, was also about MH370, and this one seems to be a revised/updated version in English.

She has been touting her theories from the beginning, and from what I understand, has discarded any and all accepted evidence and scholarship on MH370, expressing doubt that the aircraft could have turned back the way it did and that the Inmarsat data is unreliable and not public, focusing on the undisclosed cargo aboard the aircraft, and ultimately spinning a grand narrative about an international, global cover-up that is all-consuming and has 'gotten to' everyone (and therefore, she is a crusader for the truth when all others are not able to see clearly). Having discarded this narrative, the 'official' one, all further theorising on her part is pure speculation without any actual, hard evidence, as far as I'm concerned, even if she is citing circumstantial evidence or painting possible 'background' and context. Bonkers, indeed.

I think the NOK response/review posted by u/pigdead is as sceptical and balanced as it could be, but also hopeful for any traction or publicity that the book may bring to the cause of MH370.

Ultimately, any comment on the book and its claims can only be made once it is released, and I look forward to robust and exhaustive rebuttals from the scientific community and institutional experts. I also look forward to reviews/responses in the media that are not fawning or uncritical, that do not drop everything for this 'shiny new toy', which is a road we gone down many times before.