Some of the most beautiful mathematical objects found in the last forty years are the sporadic simple groups. However, gaining familiarity with these groups presents problems for two reasons. First, they were discovered in many different ways, so to understand their constructions in depth one needs to study lots of different techniques. Second, since each of them is in a sense recording some exceptional symmetry in spaces of certain dimensions, they are by their nature highly complicated objects with a rich underlying combinatorial structure. Motivated by initial results which showed that the...