I found my way to this book via a recommendation by Dr. Charles Parker, whose book New ADHD Medication Rules had a substantial positive impact on my understanding of ADHD, ability to make more effective use of my meds, and as a result, my life.
Dr. Fasano is a pediatric gastroenterologist who helped bring awareness of celiac disease to the United States amid a fair amount of skepticism from the local medical establishment of the time (it was circular: celiac was widely recognized in Europe, largely due to people going off of gluten for a time during wheat shortages in WWII; when they started eating wheat again, some people noticed issues and [fast forward several years] doctors in Europe knew to look for it, so it got diagnosed). North Americans never gave up wheat during the war and doctors in the U.S. were largely unaware of it as a condition and didn't consider it when diagnosing patients; ergo, the prevailing opinion was that celiac disease just didn't exist in the U.S.
Dr. Fasano's writing hits a nice balance, most of the time, of staying accessible while delving into the science to a satisfying degree: he doesn't oversimplify for readers or use vague/red-flag terms like "toxins" as he discusses the three gluten-related conditions covered in the book: wheat allergy, celiac disease (an autoimmune condition), and gluten intolerance/sensitivity. When multiple theories of underlying mechanisms are present, he lays out the competing theories, shares which one he leans toward and why, and he doesn't speculate without making it clear he's speculating. It's a touch repetitive in places and might have benefited from tighter editing, but it's a minor quibble. Not having any interest in making more humans, I skipped over the sections on the relationship between gluten intolerance and fertility, same for raising kids with celiac disease.
The author is very clear that individuals should not go off experimenting on their own without the care of a doctor or nutritionist. He specifically cautions the reader against going off of gluten on their own if celiac disease is present or suspected, since going off gluten can lead to a false negative test for the disease.
I didn't suspect gluten was a problem for me but did suspect that widespread inflammation was impacting my mental health and that it could be something food-related that was exacerbating extant depression, anxiety, and ADHD symptoms (which have all gotten worse since piling long COVID onto the mix). Hoping to rule out gluten as a culprit, I tried out Fasano's method--used only with those suspecting a sensitivity, never an allergy or celiac disease--to go off of foods containing gluten (that's wheat, rye, and barley) for two weeks, then resume eating glutinous foods for two weeks and see if they notice a difference.
If someone had suggested to me a few months ago that maybe I should try going gluten-free to lessen the severity of my mental health issues... depending on the day, I might have chosen violence or might have offered a lecture on how draining and obnoxious the endless litany of (well-meaning!) "have you tried -----" is for those who deal with chronic conditions or disabilities, especially when the recipients of these suggestions have been thinking about and living with, around, and through the condition for *years*.
To be perfectly, utterly clear, that has not changed: it is still obnoxious and no one should do that.
With all that said, I must--extremely grudgingly--admit some understanding of how it is that gluten-free people become the monomaniacal, crossfit-level evangelists that they have so rightfully earned a dodgy reputation for being. I did not need to go back on gluten for two weeks; I knew within 24 hours. Trust me that there is nothing short of unambiguous evidence of an immense and drastic change in my ability to function that would lead to my considering, for even a moment, giving up beer and Spätzle and sourdough. Since I wasn't expecting anything, I doubt I'm looking at placebo effect, but it can't be totally ruled out. For what it's worth, I don't believe I've found the unified field theory of my personal mental health or anything--it's not some kind of One True Answer or the whole puzzle. But it is a piece of my puzzle, and a sizable chunk at that.
I have a much better grasp of how my extreme seasonal affective disorder (causing me to, among other things, crave carbs and eat much more bread and pasta than I do the rest of the year) cycles up, amplified by a stacking inflammatory response, to the living hell of anxiety and depression I'm so unpleasantly familiar with by the time I hit February.
This is not going to be a piece of everyone's puzzle, and I'm not going to turn evangelistic about it, but this was (somewhat regretfully) revelatory for me.