This book gives a full description of the structures and symmetries of incommensurately modulated crystals and composite crystals. It also gives a complete presentaion of crystallographic methods of structural analysis of incommensurate crystals. It provides the necessary background for a skilled application of superspace methods to aperiodic crystals

1. Structure and diffraction of aperiodic crystals
2. Modulated crystals in superspace
3. Symmetry of modulated crystals
4. Incommensurate composite crystals
5. Superstructures and the commensurate approximation
6. Quantitative description of the diffraction by aperiodic crystals
7. Structure refinements
8. Electron density in superspace
9. Determination of the superspace group
10. Methods of structure solution
11. Systematic crystal chemistry
Appendices