This book was kind of like Cheetos: a dangerously cheesy grab-bag of tropes.
Don't get me wrong. I appreciate the effort by a mainstream author to write about his faith, and I think Christian themes can be worked into fiction in a way that makes it easier to get past your instinctive reactions to "religious" texts and better understand the themes themselves. But for this to work, the story must come first; otherwise you basically have a religious text that is not as rigorous or interesting as it could have been if it were not surrounded by and diluted with a flimsy framework of plot and characters.
I haven't read Dekker's other fiction, but in A.D 30, the writing itself is pretty bad. It has a lot of the stilted, pretentious, worst-of-Louis-L'amour-ish, "this character is humble and simple but thinks in profound fortune-cookie-ish insights and is actually smarter and better than everyone else" feel to it.
The characters are also classic clichés:
-oppressed and meek yet strong and liberated woman
-savage yet noble Bedouins
-crafty, lusty, evil kings
And so are the themes:
-there is nothing to fear but fear itself
-love conquers all
There's a huge amount of Christian theology worked into the story, which is good, but it's about as subtle as a felt-board Sunday-school story. Whenever we meet "Yeshua" (Jesus; for other cleverly obfuscated and thus much more mysterious proper nouns see also "Miriam" (Mary) and "Bedu" (Bedouin)), his eyes are stopping people's hearts, his presence is taking away people's breath, and he is gently yet powerfully quoting verbatim snippets from the gospels in a loosely-connected string of thought with a tenuous connection to the story.
This is awkward enough, but I understand the desire to not in any way twist Jesus' words (although I'm not sure if stringing together snippets is any less dangerous in this respect than failing to quote a modern Bible word for word). What makes it worse is that the characters go totally out of character to analyze his words the same way a modern Bible reader would, even going so far as to 'break it down to the original Greek':
[Maviah, thinking to herself]: To repent meant to go beyond one's way of thinking, this I knew also from the Greek of the same word, metanoia.
[Stephen, explaining Jesus' teaching]: "Yeshua says always: be anxious for nothing. And what is anxiousness but what the Greeks say? It is merizo, 'to divide,' and nous, 'the mind.' To have a divided mind, torn between security and fear."
But the final nails in the cheesy theological exposition coffin are the thinly veiled allusions to scripture that hadn't even been written yet:
[Maviah, to Herod, accidentally? prophesying about Jesus' trial]: "You will find no fault with him when the time comes."
[Yeshua, preemptively quoting Hebrews]: "To the Hebrews it will one day be written of me: 'During the days of Yeshua's life on earth, he offered up prayers and petitions with fervent cries and tears... and he was heard because of his reverent submission.' ... They will also write of me: 'Son though he was, he learned obedience from what he suffered.'
All in all, the book was mildly entertaining and had a good message, but trying to re-tell the story of Jesus in a fresh, interesting, non-cheesy way is a tall order, and A.D. 30 fell short.