Shelley also wrote a second novel called The Last Man, released in 1826, which is about a post-apocalyptic, plague-ravaged Earth of the 21st century, and was possibly the very first novel of that genre ever written.
"Last man" fiction was actually popular in the early 19th century; Shelley was by no means the first to tackle the theme. There's an 1805 French novel, a poem by Byron, and a painting, at least, as I recall.
War of the Worlds is the very first alien invasion book, while The Time Machine is the very first time machine in literature.
Edward Page Mitchell's "The Clock That Went Backward" precedes it by over a decade; it was published in 1881. It also invents the predestination paradox in fiction.