What is an example of literary device used in The Hitchhiker's Guide to the Galaxy?

The most important literary device in the novel is the use
of a fictional encyclopedia, which explains some of the important events and themes.
The Hitchhiker's Guide, in the book, is a real traveler's guide,
containing often-inaccurate but usually insightful information about everything in the
galaxy. This is intended to replace a larger resource, and provide fast advice for
dealing with unexpected situations. This acts as a plot point; Ford Prefect is a writer
for the Guide's publisher and was stranded on Earth while gathering
information for the updated edition.

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(Excerpt from The Hitchhiker’s Guide
to the Galaxy, Page 634784, Section 5a, Entry:
Magrathea)

Far back in the mists of ancient time, in the great and
glorious days of the former Galactic Empire, life was wild, rich and largely tax free.
Mighty starships plied their way between exotic suns...
(Adams, The
Hitchhiker's Guide to the Galaxy, Google
Books)

This is an example of
epistolary literature, in which fictional documents are used to inform or bolster the
story. Guide entries show an extremely diverse population of creatures and events,
allowing Adams to hint at an enormous, populated universe, the scope of which is far
beyond human ability to change or even comprehend.