A short book by Bear - more of a novella, really. The moon has been colonized, and society has developed into a clanlike structure of family/companies. On one of these, a man is working on scientific experiments to try to achieve absolute zero, which he believes would result in phenomena interesting to physics. His sister comes across an opportunity to acquire a batch of frozen heads, cryonically preserved in centuries past by those hoping for future resurrection. This seems unlikely, but she hopes to be able to use new techniques to reads some of these heads' preserved memories, to study anthropologially. Clinching the deal is that two of the individuals wetre the founders of their clan.
Unfortunately, unbeknownst to them, another of the heads is that of the founder of a powerful religious group (bearing more than a passing resemblance to Scientology), and that group will do anything to stop the transfer of heads from happening...
Pretty good sci-fi, the ending is a bit overblown, however.
