Small Text Size in ePub file and Code Samples lack background

## Location within the Book

* Book order number: `0098459581`
* Book build date (Is the date on page 1): 2021-06-30
* Book format (PDF, Epub or Mobi): Epub
* Chapter or Appendix:
* Section:
* Subsection:
* What operating system are you using:
- [ ] Linux (Ubuntu 20.04)
- [ ] Linux (Ubuntu 18.04)
- [ ] Linux (Other)
- [ ] MacOS Catalina
- [ ] MacOS Mojave
- [x] MacOS Big Sur
- [ ] Windows 10 Pro, Version 2004 or higher
- [ ] Windows 10 Pro, Version 1909 or lower
- [ ] Windows 10 Home, Version 2004 or higher
- [ ] Windows 10 Home, Version 1909 or lower

Hint: Page numbers change all the time. The best way to report an issue is by chapter, section, and subsection numbers.

## Description
The code samples do not change in size in `Apple Books.app` and they are missing the grey background present in the PDF version which reduces readability.

ePub is nice when screen real estate is limited or if customers want to refresh the material on-the-go. PDF does not allow word wrapping.

Thank you for taking a look at this! Been enjoying the learning journey through this book.

Here is a snippet of what the PDF looks like:

And here is what the ePub version looks like:

## Possible Solutions

## Your full name so we can provide accurate credit within the book