Sorry, but in 1929 a book cover like this would likely have been hand lettered, not typeset.

Not finding anything particularly close. Shares some characteristics with Kabel and Bernhard Gothic....

I tried in the font identification website http://en.likefont.com and there are 2111 matched fonts in total, and the most similar font is Kapra-Bold ☞.
This is my identification result page for your image: http://en.likefont.com/community/5045422/

Thank you K.C. Thompson and LiLianJie for your help!

K.C. Thompson's suggestion Kabel seems closer to me, only because of the angled terminals of the E and L. The G seems pretty special, too. And the extended horizontal bar of two of the A's in the title. I wonder if any types uses an F like the one in "Farewell"?

Martin, I searched on the title as a whole, the author's name as a whole, and then on individual letters. No luck on finding anything comparable to that F.

If you search on Google, a later (mid 1930s) German edition actually used Kabel on the cover. Your options are to find a sans serif that is close to the proportions of the original and customize it, or work backwards from Kabel.