As a matter of full disclosure, I am a freelance writer occasionally employed by Mongoose. I had nothing to do with the production of this book.
AM5: Solomani does a great job of presenting the formerly monolithic baddies of the Solomani Confederation in a more balanced and complex light. The Solomani are still baddies from an Imperial point of view, but they are here given more credible motivations, and viewpoints from fairly open-minded to severely xenophobic are examined.
The book offers new minor races, including a deeper look at Uplifted Dolphins and Apes, as seen in the Core Rulebook. The Career section could be longer, offering nothing like the selection found in previous Alien Modules. The book would benefit from more artwork, including an actual picture of the apes, although the artwork is parsecs ahead of that found in Alien Module 4: Zhodani.
Overall, this is a great read. And GMs of any system can use the info here to inform their own baddies. Just swap names and you have Cardassians, the Galactic Empire or anything else that your campaign requires.