You'd need a Summer-weight suit for this to be at-all comfortable. "High-twist wool" and "unlined" or "half-lined" are your search terms. Silk-wool blends also OK. Other fabric options for warm weather open up in some contexts (linen and linen/wool/silk/cotton blends, warm-weather cotton weaves like seersucker, maybe even rayon though that's a bit niche) but probably not if you're looking to dress for an interview at a bank in New York. Part of why suits are in-practice expensive and inconvenient (and why only-occasional wearers judge them unpleasant to wear—not unreasonably, given their exposure to them) is that you need at-minimum one set for moderate-and-lower temps ("three-season"), and another set for hot days.

I have one unlined high-twist wool navy blazer that's so cool it's actually kind of a problem because offices often have their AC cranked up on hot days. I end up needing an overcoat or second, winter-weight jacket indoors, LOL. Hold the thing up to a light and it looks like a star field seen from outside the Earth's atmosphere, dark with endless dots of light, so air goes right through it.

People who've read a couple of these books and are trying to use them are usually transparent, and it hurts way more than it helps. If they weren't inept at applying the advice, they probably wouldn't have needed it. Especially if they're not very young—if they're older and haven't picked up most of that stuff through natural observational skills and curiosity-driven trial-and-error, their odds of reading and practicing their way to significant improvement seem low.

This goes for "nonviolent communication" and similar, too. Trying to use these things if you weren't already a natural just red-flags "I'm trying to manipulate you".

"First, genuinely care" is only a little less useless than "be attractive; don't be unattractive". In practice, most of the folks with a problem in that area aren't going to read the book and do the work on that bit before trying to apply the rest. Those without such a problem, likely don't need the book.