The book “Variational approach to water wave modelling“, co-authored by Didier Clamond (Nice, France); Denys Dutykh (Kalifa, Saudia Arabia), and Dimitrios Mitsotakis (Victoria, New Zealand), has been published by the IAHR. It is a gold open access book and is freely available to researchers worldwide (link here). The book illustrates the advantage of using variational principles involving as many dependent variables as possible. Its primary purpose is to provide a generalized framework for deriving model equations for water waves. The methodology is elucidated through a range of novel examples. The screenshot below shows the front page of the book.