Reddit mentions of The Image of the Netherworld in the Sumerian Sources

Welcome to the sub, WalksWithin!

You'll likely get a much more in-depth response from Erra-Epiri when she's on next, since she's infinitely more scholarly than I am, but, I'll toss a few titles your way, and she'll fill it out for you.

First, I'm not personally aware of too many books that are overviews of Mesopotamian gods and goddesses exclusively. What I can recommend, on this subject though, is the following:

• Gods, Demons, and Symbols of Ancient Mesopotamia
  
  While it may seem a simple reference book at first, this is actually one of the most concise overviews of religious ideas and beliefs found in Mesopotamia. It has entries on deities, cities, mythological creatures, symbols, and so much more. It's very useful.
  
  Second, the real meat and potatoes concerning gods and goddesses is found in the mythology of Mesopotamia. Everything we know about them comes exclusively from the cuneiform tablets that have been excavated and translated. Here are my favorite books which cover exclusively mythology:
  
  
• The Harps That Once...
  
• Myths From Mesopotamia
  
  Third, an actual study of the religion may also be of interest to you. The following books are a bit more complex, though they can be very enlightening:
  
  
• The Treasures of Darkness
  
• The Image of the Netherworld
  
  Finally, a few general information books, which touch on religious ideas, mythology, the gods, as well as history and culture. These both come from a writer named Samuel Noah Kramer, an esteemed Sumerologist who's well worth reading:
  
  
• The Sumerians
  
• History Begins At Sumer
  
  My personal recommendation, if you're solely interested in the gods and goddesses, would be some combination of "Gods, Demons, and Symbols" + either "The Harps That Once" or "Myths from Mesopotamia" to get started.
  
  If you're willing to put a little more legwork in though, any of the other books I listed above will be very good. And, further, if you're curious, I can point you toward a number of online resources that have better information than just what you'll find on Wikipedia, or through a Google search.
  
  Once again, welcome to the sub! Feel free to ask questions if you have them.