For newcomer’s, one place to start is Marjorie Senechal‘s accessible Crystalline Symmetries. The old classic is the 2nd edition (if you can find it) of Charles Kittel‘s Solid State Physics; the curmudgeons don’t like subsequent editions as much. More recent books include Neil Ashcroft & David Mermin’s Solid State Physics, W. Opechowski’s Crystallographic and metacrystallographic groups, and Marc De Graef & Michael McHenry’s Structure of Materials: An Introduction to Crystallography, Diffraction and Symmetry. For a historical overview, see the Historical Atlas of Crystallography, edited by J. Lima-de-Faria.

For mathematical crystallography, classical works range from Harold Hilton’s 1903 Mathematical Crystallography and the Theory of Groups of Movements to Brown, Bulow, Neubuser, Wondratshek and Zassenhauss’s Crystallographic Groups of Four-Dimensional Space to Marjorie Senechal’s Quasicrystals and geometry and Mike O’Keeffe and Bruce Hyde’s Crystal Structures I: Patterns & Symmetry.

On more specialized topics …

The primary users of mathematical crystallography are likely to be in crystal engineering (especially crystal design) and crystal analysis.

See also:

  • Earle Ryba‘s list of books.