'The Book' for me was a series - The Chronicles Of Narnia.
I was a voracious reader from a young age, and devoured book after book, but it was this series that truly transported me to another world.
I lived and breathed the series every spare moment, dressing (at home) as I thought a Narnian would dress, and even eating foods I thought they might eat. I yearned deeply to be transported there, and a small part of me will be forever disappointed that I haven't been.
The other 'The Book' for me is the first book my husband bought me - a beautiful edition of The Hobbit, that included a recording by JRR Tolkien himself reading the part where Bilbo meets Gollum, a stunning map of Middle Earth and postcards with beautiful illustrations. Husband had wanted to get me a special first present, but was a little surprised when I burst into delighted tears and couldn't speak I was so overwhelmed. I knew for sure then that he was 100% the one for me.