That first novel was promising, although it does not stand up as well as the critics thought it would, but it's definitely been down hill ever since . . Nay. Armies of the Night and Miami and the Siege of Chicago were far superior to NATD.
That Mailer has several Spaniards in his brainworks was ALWAYS obvious to friends, foes, and Mailer himself; the problem is he has always chosen to display the Spaniards, FULL FRONTAL!
But they were not novels, for one thing. And while they were well written he was completely wrong about the Viet Nam War and played the role of the ideal communist directed useful idiot, just as Ho Chi Minh intended in taking a leaf from his master Mao. See the wonderful summary of Ho's skill in this regard in J.J. Servan Schreiber's "The American Challenge."