In 1911 a book was published by an American missionary who traveled across Arabia and had visited Yemen as early as 1890 when the British were in control of Aden. In 1893 he was able to go as far as Sanaa under Turkish control at that time. This travel account is probably written for kids, but it does provide an interesting glimpse of Yemen over a century ago from a prejudicial "Western" point if view. The book is available online, but I attach here the pages on Yemen.
Camel market in Aden ca. 1911