This book by John Rupert Martin is a good introductory book in the understanding of Baroque artists and their tremendous variety.  Martin defines the Baroque characteristics, but only very broadly leaving a significant amount of room for the reader to make his own deductions.  In general, Martin believes that the typical definitions of the Baroque are "too restrictive and hence likely to create more problems of classification and interpretation than it solves."  Even the time of the Baroque is left open to the reader when Martin says the Baroque is roughly comprehended by the seventeenth century.  It is important to note at the outset that this is only a convenient approximation;  for epoch as a whole can certainly not be fitted into such a strait-jacket."  This helps to define the Baroque much more generally as a gradual change which can much easily...