The best book on the Walashma dynasty is a book written by the scholar Al Maqrizi in 1436 called الامام الاحبار من الأرض الحبشة الى ملوك الاسلام(The book of the true knowledge of the History of the Muslim Kings in Ethiopia), which includes a section on the geography of the Islamic kingdoms of al-Habasha, a section on the Zeila region (the heartland of the Walashma kingdom), and a third section detailing the history of the Walashma dynasty.
A century prior to al-Maqrizi, Ibn Khaldun mentioned the Walashma dynasty and the Islamic lands of al-Habasha in his "History of the World",
Ifat Kingdom is also a medieval kingdom between the 13th and 15 the century.
Read the history of Ifat kingdom in the following references:
J. Gordon Melton and Martin Baumann, Religions of the World, Second Edition: A Comprehensive Encyclopedia of Beliefs and Practices, page 2663
Richard Pankhurst
The Ethiopian Borderlands: Essays in Regional History from Ancient Times to the End of the 18th Century - Google Books" The Red Sea Press, 1997. p. 40-45.
Mordechai Abir (2013).
Ethiopia and the Red Sea: The Rise and Decline of the Solomonic Dynasty and Muslim European Rivalry in the Region. Routledge. pp. 25–27.
ISBN 978-1-136-28090-0.
Ewald Wagner (1991), The Genealogy of the later Walashma' Sultans of Adal and Harar, Zeitschrift der Deutschen Morgenländischen Gesellschaft, Vol. 141, No. 2 (1991), pp. 376-386
Fage, J.D (2010).
"The Cambridge History of Africa: From c. 1050 to c. 1600".
ISIM Review. UK: Cambridge University Press (Spring 2005): 146–147.
Most of these books mention ifat kingdom, that's it.
Adal kingdom:
Someone wrote a comprehensive report on Adal Sultanate. This is the link:
https://hiiraanblogs.wordpress.com/...geez-አዳል-ʾadal-arabic-سلطنة-عدل-c-1415-1577/