The main course reference is Parameterized Algorithms by Marek Cygan and co-authors (2015).
The published optional references include Parameterized Complexity by Rod Downey and Michael Fellows, Parameterized Complexity Theory by Jörg Flum and Martin Grohe, Invitation to Fixed-Parameter Algorithms by Rolf Niedermeier, and Kernelization: Theory of Parameterized Preprocessing by Fedor Fomin, Daniel Lokshtanov, Saket Saurabh and Meirav Zehavi.
Original NPTEL course description and bibliography
These are reference links; no textbook files are copied into this archive.