Decorative - perhaps not quite classic art-deco, yet definitely decorative art.
This is the cover of a small booklet about succulants. I.e. a practical guide to keeping these plants. Part of a larger series of practical guides on a wide array of subjects - 'knowledge and ability'. No date in the book anywhere, but the spelling places it in the early 1930-ies (Dutch spelling evolves rather).
This is a textbook, an introduction into physics aimed at 11 year olds. Titled 'thinking, finding and appying'. The styling definitely evokes the late 1920-ies, yet this revised 15th printing actually dates from 1953.
(Well, actually also informative; everything in these books still true and valid.)