I Am Legend by Richard Matheson can be found on Google Books.
Previous adaptations
1 1964 The Last Man on Earth
2 1971 The Omega Man
3 Some low budget movie that most people never heard of
The creatures were vampires in the book but this adaptation only slightly depicted them as vampires. I didn't see this movie as a horror or even a scifi. So I didn't watch it expecting a Dawn of the Dead or 28 Days. I'm sure the DVD will have some of the cut scenes in it and perhaps the sequel will show us what happened after the lady reached the survival camp. Except the sequel couldn't have Will Smith--maybe there won't be a sequel after all.
Almost every movie has a cliff hanger, for example the most recent Resident Evil left us wondering how she's gonna get the world back.