I would toss the book away. It sounds like pseudo-scholarship. Look at the end of the book and note the relative paucity of footnotes.
Is Winkler credible? While he had some sort of Orthodox education, he also studied with Schater-Shalomi and now declares himself "non-denominational". A brief review of his career indicates he aligns himself with various new-age types such as Andrew Weil and Deepak Chopra. I don't see any academic credentials- where did he study? Where did he get his PhD? Has he published anything in a respected peer-reviewed journal? I searched "Google Scholar" and came up with ZERO articles written by him!
This forum is not the place for editorializing, so I have done my best to limit my critique to the above questions. But the bottom line is, that it's not up to me to prove Winkler a fraud- it's up to him to prove his theories with real scholarship- especially when his ideas are extremely radical.
You write that Winkler claims that mysticism was downplayed in the wake of the inquisition and witch hunts. This is a bizarre claim. The most important even in the development of Jewish mysticism was the publication of the Zohar which occurred after the Inquisition had started. Note that Maimonides, the quintessential non-mystic was living far from the influences from Christianity and was completely opposed to all forms of magic and even denied that such powers actually exist. Maimonides did not reject magic due to some artificial pressure. While he may have been influenced by Greek philosophy- as famously claimed by the Vilna Gaon, that was just his skepticism of magical powers. The antipathy against magic, whether effective of not, goes way back to the Talmud and Bible- it's not a reaction that suddenly (or even gradually) popped up in the Medieval period. The fact is that mysticism does have a place in Jewish life, and has not been "downplayed heavily".
In the book, Winkler makes claim after claim and provides no source of proof whatsoever.
- The custom of naming children after family members is "probably
because of... insecurity.. It feels safer to just attach a name that
has already been proven by its having worn successfully for so many
centuries by so many others." (page 65)
- Leaving crumbs for birds on
Shabbat Shira (when the Az Yashir is read in synagogues) is
because "of the songs they teach us." (page 69)
- Ritual slaughter requires "spiritual consciousness". (page 166)
- "The word kosher in fact means "prepare", as in preparing the spirit [of the animal] for release" (page 166)
- Most of today's kosher meat is probably not "actually kosher since it's highly unlikely that such mass slaughter can be performed... with little of no discomfort to the creatures..." (page 168)
- "Many of the twelve tribes.. carried specific animal
powers" (page 171)
These are just a few of the many claims that Winkler presents as facts without any evidence. Until he writes likes a scholar and provides sources, and avoids speculation, I see no reason why anyone should take anything he writes seriously.
I regret that I haven't answered your question as to which books are recommendable. But I think it's just as important to avoid wasting time with phony scholarship.