The Kindle Publishing Guidelines have this to say about monospace:
3.1.6 Text Guideline #6: Monospaced Font Is Supported
Kindle uses a default font for content if none is specified; it also supports a monospaced font.
Kindle uses the monospaced font to render content in the following tags: <pre>, <code>, <samp>,
<kbd>, <tt>, <font face="courier">, <font face="monospace">.
With the exception of <pre>, the tags listed above do not change the text alignment. If the content in
these tags should be left-aligned, wrap the tags listed above in a <div> styled with CSS using textalign:left.
Publishers can include their own font for their content. Amazon has a quality assurance process to ensure
that these fonts display well on e Ink-based devices and do not impair the reading experience. Do not
include the Charis font; it is replaced with a higher quality font in the Kindle Readers.