Gate Crashers

This is a great, serious SF adventure with a big humorous element, but without the heavy-handedness of Hitchhiker's Guide to the Galaxy.

Humor is hard to do, especially in speculative fiction. Generally, it comes off to me as trying too hard to be funny, and just ends up being cringeworthy. But I found this novel to be refreshingly light-handed and deft with the humor, while still delving into serious themes, such as humankind's arrogance, colonialist tendencies, and obliviousness to the implications and aftereffects of their actions.