The central idea of this theory, fixed-parameter tractability, has led to the development of various techniques of new algorithms and new theories throughout intractability. This book is the introduction of state-of-the-art algorithms for both techniques for fixed-parameter tractability and complexity theory the class of structural parameters, and presents detailed evidence of the recent progress that has not appeared in book form before. Several chapters each devoted to intractability, the algorithm technique for designing fixed-parameter tractable algorithms, and restricted fixed-parameter tractability and subexponential time complexity.