I also think book Stannis is good, and not at all boring or humorless. Certainly, he has a gloomy personality and is easy to anger. But his snappy remarks are almost always clever and shows that Stannis understand the irony of things better than most.
Some quotes:
"Her own father got this child on her? We are well rid of her, then. I will not suffer such abominations here. This is not King's Landing."
"Without a son of Winterfell to stand beside me, I can only hope to win the north by battle. That requires stealing a leaf from my brother's book. Not that Robert ever read one."
"Robert could piss in a cup and men would call it wine, but I offer them cold clear water and they squint in suspicion and mutter to each other about how queer it tastes."
Davos: "I do not know this Lord of Light, but I knew the gods we burned this morning. The Smith has kept my ships safe, while the Mother has given me seven strong sons.
Stannis: Your wife has given you seven strong sons. Do you pray to her? It was wood we burned this morning."
Davos: "Give me knights as heralds...-"
Stannis: "I could give you those men, yes, I have at least a hundred knights who prefer reading to fighting."
Renly: "You'll be pleased to know she came to me a maid."
Stannis: "In your bed she's like to die that way."
"Weddings have become more perilous than battles, it would seem."
"Everyone else has seen the thing, why not a blind man?"
"You haggle like a crone with a codfish, Lord Snow. Did Ned Stark father you on some fishwife?"
Janos: "Who better to command the black cloaks than a man who once commanded the gold, sire?"
Stannis: "Any of you, I would think. Even the cook."
Asha: "Your Grace's royal brother was renowned for turning fallen foes into friend. Make me your man."
Stannis: "The gods did not make you a man. How can I?"
"Half my army is made up of unbelievers. I will have no burnings. Pray harder."
"You chatter like magpies, and with less sense"
So many good gems to choose from.