"You don't think nirvana, the cessation of desires grounded in the proliferation of concepts is the Buddhist's ultimate goal"

It is. But it is not void and does not result in tranquil detachment.

Do you think Thomas McEvilley's The Shape of Ancient Thought is a "misguided source" on Buddhism?

This is the first time I've heard abut it. So, I quickly skimmed through it and searched for nirvana.

Very first hit reads: "... in the early Buddhist view Nirvana is an “invisible infinite consciousness shining everywhere,” which becomes the consciousness of the enlightened yogi." There is also this bit: "The Digha Nika-ya says of nirvana, “Here it is that the conditioned consciousness ceases to be” (D.I.223). The state of nirvana is that of the person who has gained “mental freedom”—that is, freedom from conditioning—yet continues to live out his or her life."

That's pretty much it and is as far from your "void of nirvana" and "detachment" as one can get. I don't know what conclusions McEvilley draws from all that info, so I can't pass a judgment as for how "misguided" his book is or is not. But if you have based your interpretation on him, he either makes wrong conclusions or you didn't understand what he has written.