The Borgia Blade
I know of Gardner Fox mostly through his comic creations (like, say Hawkman or the Justice Society of America) and the sword-and-sorcery adventures of Kothar. The Kothar stories are mild entertainment. They alternate moments of splendid action and inventiveness with head-slapping stupidity and nonsense. I once resolved to finally read through the entire series — they’re short books, after all — and mid way through the second book remembered why I hadn’t gotten any further.
But Morgan Holmes knows his heroic fiction, and when he told me there were some good Gardner Fox historicals, I believed him implicitly, and snapped up the three he said were the best. One of these, The Borgia Blade, I took with me to read on a long plane flight recently, and the competence of the writing and the depth of the characters surpassed anything that I’d expected from the creator of Kothar.