Do yourself a favor and check out The Future of Us by Jay Asher and Carolyn Mackler. It's billed as YA but anyone who uses Facebook/social media will appreciate it, and, as I say below, especially if you remember a time before the internet was a part of our daily lives. If my review sounds vague, it's because I tried hard not to give anything major away. You should read it for yourself, it's that good.
I cannot say enough good things about this book, especially if you're around the age of the protagonists and if you remember AOL and dial up internet. You're likely to enjoy it if you're a teenager, too, but for those of us in that age group (I'm 36), the idea of what the internet has the power to do works its spell in this page-turner.
Emma and Josh are best friends; Josh used to have a crush on her, but they've (mostly) moved on. One day, Emma logs on to her new AOL account and discovers something called Facebook. She and Josh try to puzzle over what exactly Facebook is and why their future selves are writing pithy, strange comments for all the world to see. What gets strange very fast is that Emma discovers that she can actually directly change her future by very minute actions in her present, and she becomes obsessed with doing so. Without giving too much away, the idea that everything we do in the present has a long-term impact is fascinating and disturbing, and each has to explore what they'd want their future selves to know about them, and how far ahead they intend to map out their lives. Soon Emma especially winds up so fixated on the future she forgets about the present. The novel unfolds wonderfully, with alternating viewpoints, and I found myself wanting to reach in and say "No, don't do it!" multiple times. I especially liked that the authors didn't present one future self as necessarily more perfect than any other; in their world, each was as plausible as another, and Emma and Josh had to determine for themselves, often through trial and error, what kind of life they envisioned.
The idea of knowing exactly what we'll be doing any given amount of time from now is miraculous or terrifying, depending on who you are (I vacillate between the two), and The Future of Us plays up that tension to the max, while highlighting the secret online universe the two have discovered. This book speaks to adults just as much, if not more so, than teenagers, and its message about living in the present is inspiring, without ever being preachy. I found myself rooting for both Emma and Josh even when they clearly made missteps and hurt others (or themselves). Mackler and Asher did an amazing job and while the ending is perfectly summed up, I'd love to see a sequel because I didn't want to stop reading! You will likely wind up questioning some of your own Facebook and social media usage as you read, wondering what the purpose is, as the protagonists do.