If you like The Hitchhiker's Guide to the Galaxy by Douglas Adams

  We hope you enjoy the following titles as much as you enjoyed The
Hitchhiker's Guide to the Galaxy.

The Wee Free Men by Terry Pratchett.
A young witch-to-be named Tiffany teams up with the Wee Free Men, a clan of six-inch-high blue men, to rescue her baby brother and ward off a sinister invasion from Fairyland.

The Sterkarm Handshake by Susan Price.
Having traveled to a sixteenth century border clan in England through a tunnel created by a twenty-first century company, Andrea must decide in which era she will live.

Angus, Thongs And Full-Frontal Snogging: Confessions of Georgia Nicolson by Louise Rennison.
Presents the humorous journal of a year in the life of a fourteen-year-old British girl who tries to reduce the size of her nose, stop her mad cat from terrorizing the neighborhood animals, and win the love of handsome hunk Robbie. [first in a series]

5 Novels by Daniel Pinkwater.
This includes Alan Mendelsohn, the boy
from Mars -- Slaves of Spiegel -- The Snarkout boys and the avocado of death -- The last guru -- Young adult novel. Pinkwater has a very
quirky sense of humor, so if you like one of these, you'll like them
all.

The Curious Incident of the Dog in the Night-time by Mark Haddon.
Despite his overhwleming fear of interacting with people, Christopher, a mathematically-gifted, autistic fifteen-year-old boy, decides to investigate the murder of a neighbor's dog and uncovers secret information about his mother.