The Libyan historian Hadi Bulugma produced a series of books in Arabic on the history of Benghazi entitled بنغازي عبر التاريخ. He also made an abbreviated English version, the first volume of which (I am not sure that the second and third volumes were ever finished) concentrates on the geography and geographical history of the city. Here is a PDF of the book.
Bulugma, Hadi. 1968. Benghazi through the Ages. Volume I. Dar Maktabat al-Fikr, Tripoli.