I have been doing some serious reading on animal intelligence and behavior: "Animal Cognition" by Clive Wynne, "Animal Intelligence" by Zhanna Reznikova, Animal Learning & Cognition 3rd Ed by John Pearce, and The Ethology of Domestic Animals 2nd Ed by Per Jensen. This ranks right up there with Dr. Pearce's book. Sara Shettleworth is far more open-minded than Wynne, who projects his own limitations onto the animals. She writes with the detail of Reznikova and the clarity of Pearce. If you know these authors, I have told you enough. If not, let me just say that this is one of the best detailed introductions with graphs and charts, and written in everyday language. Yet she does not wear her scholarship lightly.
However, if you are interested in bugs, Reznikova's Animal Intelligence would be my best recommendation. Or if a negative assessment of animal intelligence would make you feel better about yourself, try Dr. Wynne's "Animal Cognition" or the popular level, "Do Animals Think?" His answer is No.
Also worth reading:
Animal Minds by Donald Griffin
Minds of Their Own by Lesley Rogers
Wild Minds by Marc Hauser
The Smartest Animals on the Planet by Sally Boysen
Some of these are more-or-less popular level, mass publications. The Boysen book is a beautiful coffee table item with color photos and excellent charts and explantions of animal "IQ tests."