The book "Functional Data Structures in R" offers a comprehensive introduction to functional data structures using the R programming language. It is aimed at experienced programmers who want to enhance their skills in algorithmic programming. Readers will learn how to write more efficient code and improve the performance of their programs by engaging with the nuances of functional programming. A central theme of the book is the handling of immutable data, which means that traditional approaches to data manipulation are not applicable. Instead, techniques are presented for creating new versions of data structures rather than modifying existing ones. This is particularly relevant for applications in the fields of Big Data, finance, and data science, where efficient algorithms are crucial. By the end of the book, readers will be able to make informed decisions to work optimally with data structures without modifying the data itself.