On May 23, 2017, I posted links to buy Memento Mori from Amazon and from Barnes & Noble. Temporarily, these paperbook books were not available from these retailers. Now they are, so I will repeat the links:
The paperback can be ordered online
from Amazon by clicking
https://www.amazon.com/Memento-Mori-Ellen-Foster/dp/1300241594/
or from Barnes and Noble by clicking
http://www.barnesandnoble.com/w/memento-mori-ellen-foster/1113742062