(I got a copy of this book from the publisher through NetGalley, in exchange for an honest review.)
I can't say I liked this novel. Although the premise grabbed my attention, the story turned out to be too overdone to my liking. It partly had to do with the source of H.A.L.F. 9's non-human side. It reminded me of what I'd call "Cold War era stories": books, movies, comics tackling matters that were relevant a few decades ago (the way the Cold War provided an excellent building-ground for tense stories), but aren't so much anymore. As a result, making them interesting rather than "it's just another version of..." has become more difficult. Unfortunately, in my opinion, The Deep Beneath didn't manage to get off the ground, whether in theme or in execution.
The characters remained too flat for me to warm up to them. I expected Erika to be more of a free mind—a proud, independant young woman riding her motorcycle through the desert—and not so obsessed with her love interest that she didn't want to love because it would impede her freedom, but wait, she still keeps daydreaming about him and sniffing his scent. What could have been a good subplot, filled with questions about whether loving someone will set you back or allow you to soar, whether it will only shackle a person or not, got lost in the flow of teenage hormones. And when she opened her mouth, when she stood her ground, it was too often at the wrong moment, using the wrong words (at the 70% mark, I filed her as Too Stupid To Live).
Both Ian and Jack seemed to exist as background elements only, and never developed into actual characters with actual personalities. Sturgis had too much of a gloating villain edge, both cruel at times yet inexplicably powerless at others (in the way of the Villain Decay trope). Alecto's budding thoughts and dilemma regarding H.A.L.F. 9'got lost somewhere along the road, when it could've been such an interesting thread to develop. As for H9, I guess he was alright, in the way he discovered the outside world and grew to care for the humans he had met, but here comes the third breaking part for me: the writing.
The writing was of the "tell, not show" varity, which quickly made the story feel as dry as the desert it was set in. I can definitely say that had H9's growth been tackled in a different way, instead of that somewhat clinically detached tone, I would've appreciated it much more. Being detached made sense when it came to his stilted dialogue, since he had never been given the chance to communicate much with human beings; however, it wasn't palatable when all his thoughts and actions were described that way.
Conclusion: a story that had potential to provide food for thought, yet didn't in the end. 1.5 stars