The Assyrian Dictionary of the Oriental Institute of the University of Chicago (1921-2011)
home page with links (the download button is for free pdfs of each volume)
This may be the book with the most limited interest I've posted but couldn't resist. The 21 volumes of this monumental dictionary took 90 years to compile - the story was covered by the BBC. Every volume is available as a free download in case you want to try your hand at translating Gilgamesh or the seemingly endless Babylonian charm and spell texts. (The "Assyrian" of the title is really what's now called Akkadian as explained in the volume 1 introduction.) The authors followed the OED and included detailed examples of usage though in brief excerpts that can seem almost like a modernist poem, a rough shadow of Pound's Cantos perhaps.
I could not be in Babylon to take the loyalty oath
my soldiers drove the king of Mitanni from Nuhassi
PN took away three "hand" oxen
I dispatched the ten talents of copper on my own