I really dig the hardboiled sf/mystery style (Lethem also does this really well). After Halting State, all the violence and action that Morgan packs into his work was especially welcome. It's not great literature, but it's a fun ride.
I have this massive fear of being trapped. Trapped underground in a tight cave. Trapped under the ice (not that I have ever seen a really frozen lake or pond - I'm a Florida boy). Trapped in my own body, mind alive but unable to move (China Miéville's books tap into some of that, especially some of the punishments in the Bas-Lag novels). So Morgan's vision of mind being kept "on the stacks", frozen in time or manipulated by anyone who can afford the technology, really gave me the heebie jeebies.
Not to mention all the brutality in Altered Carbon. Now, this isn't packed full of detailed violence like Chung Kuo, by David Wingrove, but he does linger on some pretty fucked up torture a time or two. I don't have a problem with that. It fuels the rage behind the story, and who among us isn't a little fascinated by blood and gore?
All in all, a dark, flowing cyberpunk adventure. I thought I knew the answer to the whodunit early on but turned out to be wrong - a good thing, indeed. I look forward to reading more in the series.