Over the years, I've found that I enjoy books in various formats. I've been a member of Audible for many years (disclaimer: I work for Amazon.com, which is the parent company for Audible), and the eBook revolution has definitely made an impact in my reading habits. The more I like a book, the more different formats I'll end up buying it. Based on that alone, my all-time favorite book must be A Wrinkle in Time by Madeleine L'Engle.
I grew up with parents who read, particularly my father. Everyone in our house tended to wander around with books in hand, which meant the question "Where's my book?" was asked on a regular basis. My dad was the one who was big on science fiction and fantasy, along with military fiction, and his enthusiasm spilled into my reading choices. A Wrinkle in Time was the first science fiction book I remember reading, and it was pivotal for me.
It wasn't until years later that I realized just how the book had affected me. It has a female protagonist - something unique in the world of speculative fiction of the 1970's - and she's realistic. Let's be honest, Meg Murray isn't exactly what most girls would aspire to be - she's unattractive, obnoxious, scared, whiny, and something of a brat. At the same time, she does what needs to be done, even if she fights it along the way. She wants to save her father and her little brother, and make her life as close to normal as it ever was. It's something that most teenagers can relate to, even if the various worlds and space travel that she takes to get there are a little outside of most people's experiences.
This is the kind of book that holds up well over the years, and I find myself rereading it on a regular basis. I definitely recommend it, particularly as an introduction to science fiction.