A novel by Julio Cortazar. Published in 1977, the book is set in Paris and Buenos Aires.
155 chapters (some of them shorter than a printed page) make up the text. As a sample, you can read Chapter 82: "Why am I writing this ?".
The author invites the reader, in the "Tablero de Direcciones" that appears at the very beginning of the book, to make a choice:

In its own way, this book is many books, but mostly it is two books. The reader is invited to choose one between the two following possibilities:

The first book is read in the customary way, and ends at chapter 56, at the end of which three obvious little stars are equivalent to the word "End". Consequently, the reader will - without any guilty feelings - omit reading what follows.

The second book is read beginning at chaper 73, and following afterwards in the order indicated at the end of each chapter. In case of confusion or of a failure of memory, it will be sufficient to consult the following list:

73 - 1 - 2 - 116 - 3 - 84 - 4 - 71 - 5 - 81 - 74 - 6 ...

The ellipsis is mine; Cortazar provides two alternate, and equally valid since they are authorial, readings of this book that recounts the life in Paris and Buenos Aires (with a brief interlude in Montevideo) of Horacio Oliveira, possibly a writer, certainly a man given to fierce introspection.
Oliveira is presented, more than in his actions, in his interactions with Lucia (that he usually calls The Magician), their circle of peculiar jazz-loving acquaintainces in Paris and his old friends in Buenos Aires; Traveler (a man that never travels, much to his frustration), his wife Talita and the long-suffering lover Gekrepten.

This is not a very easy book, but I find it readable: I wouldn't want the "experimental" idea of a mildly ante litteram interactive book to scare off any perspective reader.
It also has some very funny parts, my favourite one being chapter 41 where a fully absurd (and possibly dangerous) situation develops in a very rational way --- and with constant overtones of seduction. The book includes extensive fragments of other books, some real some fictional. The best parts are the extracts from Ceferino's book on a new organization for the world.

Rayuela is a children's game, known in English speaking countries as hopscotch, and in Italian as "mondo" or "settimanella".