Four titles in the ""Knowabout"" series, designed to introduce mathematical concepts. Each develops an idea through a simple text combined with unusually attractive color photos, leading from a basic concept to ways the child can explore it further. Pattern is the best of these, with a mind-expanding array of patterns seen in architecture and the natural world as introduction to repetitive decorations and patterns a child can generate. Sorting also encourages participation, as the reader groups pictured objects in more than one way: by color, size, function, etc.; the idea of a set is also introduced. Length includes both the English and the metric systems and is adequate, although the subject seems slight for a whole book and the vocabulary and concepts introduced seem more miscellaneous. Capacity, while also adequate, is least successful: as the book points out, the only way really to understand differing capacities is to experiment with real containers. A useful, high-quality series to use with young children. Photos by Chris Fair-clough.