Finished up reading Halo: Cryptum. I initially read this not too long after it was released, but I never did get around to reading the sequels and, in the time since, had forgotten a lot of the details. Now with it fresh in my mind I'm ready to jump into Primordium.
Gotta say, I really loved Cryptum. It's vastly different than the earlier Halo novels, but it tackled material that I never thought I would see fleshed out in such a way; there are so many ways that a story in this era could have been done poorly, but with Cryptum Greg Bear and the folks at 343 were able to craft the beginning of a tale that feels absolutely essential to the Halo universe's overall mythology.