Photos in Craig's book are B/W and not always of very good quality. The book lists numerous species, many of which have been synonymized in later years. For each species the characteristics of the plant body, tubercles, areoles, spines, flowers, fruits, etc. are given. Other features given are the distribution and the type locality.
There is no information about minimum temperatures or type of habitat in the book.
I would not consider the Craig book very useful for identifying unknown Mammillarias.
Wolter ten Hoeve, Assen, The Netherlands.