Couldn't quite find out if this was a good or bad question from the rules, so feel free to remove it if it violates anything.
Asking for resources is totally fine here! You may also want to check out our books and resources list, although I'm not seeing anything Assyria-specific at a glance.
If you have access to the Cambridge Ancient History series, at a Library or perhaps an online resource, it's really good. It's a rather pricey series to own on your own though.
That being said, this is the part that deals with the Assyrian Empire http://universitypublishingonline.org/cambridge/histories/ebook.jsf?bid=CBO9781139054294