Here are two data points from original editions that I am fortunate to own (my late father was an architect and a big fan of Wright). I'm not suggesting that you slavishly follow the format of FLLW's own books, but at least this is instructive, since both books were produced with his blessings and participation:

When Democracy Builds, Univ of Chicago, 1945
An American Architecture, Horizon, 1955

Both books use Futura for display set in all caps, and Baskerville for text. Curiously, there are a few instances of what looks like Kabel that managed to sneak in (cap Y has fully slanted right stroke, and G looks like Kabel, although I suppose it may be some other design. In any case, a very minor thing.)

One interesting aspect of these designs is the use of Futura in two simultaneous modes: on a typical page, you'll see a running head in a dark stripe of smaller letterspaced Futura Bold, and in the midst of the light gray plane of text, an A or B head in larger Futura Medium set absolutely tight and solid. (My eye looks at these and immediately wishes they had letterspaced it a little bit at least, just to equalize interletter space, but it was clearly a very deliberate choice.)

The title pages use Futura. The 1945 book has letterspaced Futura Bold for the title, with smaller Baskerville all caps for author and publisher. The 1955 book has a very memorable design: the spread has a large b&w portrait photo of Wright as frontis, seen from the side with his gaze directed toward the gutter, and opposite this is four lines of Futura Medium all caps, widely letterspaced, in horizontal stripes going from the gutter right out to the edges of the paper (rather than conforming to the limits of the type page).

Hope this is of some use. The fact that two books ten years apart share a number of the same characteristics makes me think this is aligned with his own tastes (or at least he agreed with what the publisher presented to him).

Neutraface by House Industries.
http://www.houseind.com/index.php?page=showfont&category=&id=18#18

Bruce, sadly I can't reach these books that you are reffering. i have only Zadar's public library. ( if it is not a bad, could you post some scans or photos of pages). Thanks.

Pieter, I forgot about neutra. hehe.

Maybe Gotham or Malmo sans?

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golden ratio of passion. sansogno.coastaldisturbance.com

What about something from here?