My husband and I picked up I am Legend after seeing the movie of the same name. The movie was SCARY!! I like sci fi but I'm not a big horror fan. Writing in the 1950s, Matheson's book is suspenseful, but not gory like more modern horror has become. Part of what interested my husband and I in picking up the book was the quote on the back, "Books like I am Legend were an inspiration to me." - Stephen King.
My husband loves classic science fiction and is always curious to see how it holds up over time. He has become quite knowledgeable about post-World War II era books. I am Legend clearly fell into that category. He read the whole book - which includes the I am Legend novella as well as a handful of Matheson's other short stories. He guesses that some of the other stories have been adapted over time to be storylines in X-Files or various other sci fi shows. Personally, having read one or two of the short stories they really didn't hold my attention. But I digress...
I read I am Legend curious to see how much had been changed and adapted to turn it into a 21st century film starring Will Smith. Like many adaptations recently, there were scenes that were word for word identical to the book. Then there were entire plot arcs that had absolutely nothing to do with the original story. The long-term outcome of the movie and the novella were completely different. So much so that the purpose of the title had to change between the two formats.
Matheson's decision to write about vampires in the 1950s - much before our current Anne Rice/Buffy obsession with the creatures - made for an engaging story. In good science fiction style he relies heavily on a biological, scientific explanation for his plot - at times going into too great a detail. But, at the final moment, I would have to say, I liked Matheson's finale better than the Hollywood version. It led to a much more introspective ending. I put the book down with a "Hmm." I always like a book that makes me think.