Are we living in a computer simulation? And, if so, how could we tell? This question became very popular in the last few years and has led to many articles, comments, and arguments. The simulation hypothesis which states that all of reality, including the Earth and the observable universe, could, in fact, be the result of a computer simulation is a hot topic of debate among philosophers, scientists, and SF writers. Even the popular Saturday Morning Breakfast Cereal (SMBC) webcomic has helped clarify the issue, in a very popular strip. Greg Egan, the master of realistic SF, may have taken the matter to its ultimate consequences, with Permutation City and Instantiation, but the truth is that this question has been the subject of many books, including the famous Neuromancer, by William Gibson.
Still, to my knowledge, Simulacron-3, by Daniel Galouye, may have been the first SF book to tackle the issue head-on. For a book written more than half a century ago, the story is surprisingly modern and up-to-date. Not only the presentation of the simulated reality world is very convincing and the technology very believable, but it also turns out that the reasons why the simulated reality world (Simulacron-3) was created could be sold as a business plan for any ambitious startup today.
There is not much more that I can write about this book without depriving you of the pleasure of reading it, so let me just recommend that you get a copy from a website near you and take with you for the summer holidays.