I can recommend Frans de Waals' latest book "Are We Smart Enough to Know How Smart Animals Are?". It's an easy read that gives you an overview of the kind of an

I can recommend Frans de Waals' latest book "Are We Smart Enough to Know How Smart Animals Are?". It's an easy read that gives you an overview of the kind of animal intelligence research that is being done and how it evolved over time. It covers a wide variety of species, not only primates. It's a reasonable reflex to look for intelligence in animals that are closest to us. But I think I can relate with what you are saying. Although it makes sense in the historical scheme of things, we are generally still convinced that humans are superior to animals. While that might be true for some cases, there is a lot of research that has shown us that animals, not only primates, can surpass us when it comes to specific cognitive tasks. We're probably the best all rounders intelligence wise, but we're definitely not the best in absolute terms. The title of de Waals book encapsulates exactly that and much more, but you'll have to read it to figure that out ;)