A q-clan with q a power of 2 is equivalent to a certain generalized
quadrangle with a family of subquadrangles each associated with an oval
in the Desarguesian plane of order 2. It is also equivalent to a flock
of a quadratic cone, and hence to a line-spread of 3-dimensional
projective space and thus to a translation plane, and more. These
geometric objects are tied together by the so-called Fundamental Theorem
of q-Clan Geometry. The book gives a complete proof of this theorem,
followed by a detailed study of the known examples. The collineation
groups of the associated generalized quadrangles and the stabilizers of
their associated ovals are worked out completely.