I recently finished John Biggin's fiction book A Sailor of Austria (book 1 of a 4 book series).
Biggins weaves into his narrative the historical perspective on the Austro Hungarian Empire, and for me, illuminated just how all those diverse peoples/tribes/religions related to each other and their Empire. It was most illuminating when at the end of the War and the Hapsburg's empire crumbled, how those disparate peoples virtually turned on each other.
I recommend this book also because it gives an account of 'the other side's' activities during WW1, a perspective not as commonly addressed.
(And I hadn't realised that Japan's navy was in the Mediterranean and the Adriatic!!)
Edit
Thanks to issybird who I'm fairly sure recommended this series to me some time ago now.