Errata

4 minor mistakes:

1. no 'const' added to runApp(MyApp())
2. constructor doesn't have 'key' parameter (flutter recommends it and it was also there in your other codes)
3. Flutter info: 'bodyText1' is deprecated and shouldn't be used. Use bodyLarge instead. This feature was deprecated after v3.1.0-0.0.pre
(same for bodyText2, bodyMedium is recommended)
4. You pass title: 'Flutter and Dart Cookbook' to the widget, then you never use it

On github, the source codes do not match the chapthers (ex10-1.md should be 10-2, and ex10-2 should be 10-1.md).

Quote from the section Discussion: "The example code makes use
of a media query"

But it actually doesn't. Global variable screenHeight is initialized, then in the MyRichText class it gets assigned a value by MediaQuery, but it's never referenced afterwards and the code doesn't make use of it:

double screenHeight = 0.0;
class MyRichText extends StatelessWidget {
const MyRichText({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
screenHeight = MediaQuery.of(context).size.height / 3;
...

You have a whole class in your code, right at the beginning, which is never used:

class ListTileItem {
final String monthItem;
const ListTileItem(
this.monthItem,
);
}

You never actually created any ListTileItem instances.

Yet again, the same 'ListTileItem' class as in the previous section code is never used.

But maybe more importantly, you seem to be missing some important explanations, like why ListTile is not used with this ListView (compared to the previous section with the vertical list). Why isn't it enough to just change it to scrollDirection: Axis.horizontal, and leave everything else as it was in the previous section. I think this question comes to the serious reader's mind right away, and I myself of course researched it, but I think it would help your readers a lot if you elaborated on this in your book.

In your code due to the missing constructor, default constructor is added automatically, therefore const is not possible this way:
---
void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
...
---
RECOMMENDED (added constructor, now myApp can be const):
---
void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
...
----

And once again the argument 'Flutter and Dart Cookbook' is passed to the widget (as String title) and never used. This really is confusing for beginners, as it might not be clear to them that this 'title' is not at all the same as the other 'title' parameters in the widgets. I think with beginners (this book is for them), you must really be precise and not confuse them with redundant parameters.

You go into detailed explanation about adding the drawer to the right side, which automatically adds the back button to the left. But have you even tested your own code? The navigation drawer doesn't close when using the back button. So user doesn't even see that anything has changed unless they close the drawer manually. So you need to pop it for DemoPageFour like this:

onTap: () {
Navigator.of(context).pop(); // or Navigator.pop(context)
Navigator.of(context).push(
MaterialPageRoute(builder: (context) => const DemoPageFour()),
);
}

return MaterialPageRoute<void>(builder: builder, settings: settings);

Yet another unnecessary passed argument that just confuses the reader.
The code works fine without it:

return MaterialPageRoute<void>(builder: builder);

Yet again, passing an argument that is never used later in the class (title):
home: const MyHomePage(title: 'Flutter and Dart Cookbook')

Even the compiler warns about this unneeded print statement:
print(dataSeries.dataModel[0].title);

There is also an unnecessary 'key: null' passed in the code.

I also really don't understand why author doesn't even mention the use of 'snapshot' in the explanation of this code (or anywhere in the book), even though it is heavily used in the example code.

Missing import of:

import 'package:test/test.dart';

I'm sure this was meant to be there as this import is actually added in later tests in your book.

This import should also be explained in 6.1 where you mention:
dart pub add test --dev

After that you have this note right away:
"If you are using DartPad, you will need to use:
import 'package:flutter_test/flutter_test.dart';"

But you never mention the basic import after adding test to dev_dependencies.

Image.network('ht tps://oreil.ly/O4PEn')
(had to add space, because URLs are not allowed here)

The image is never loaded due most likely to the redirect. Same thing for the second code block in the chapter (the refeactored one). If you use the redirected final url, it works:

Image.network('ht tps://images.unsplash.com/photo-1499028344343-cd173ffc68a9')
(had to add space, because URLs are not allowed here)

I wonder if there is a quick solution to load redirected images, I haven't had any success so far.

SnickersOriginal and SnickersCrisp classes should have "mixin" rather than "abstract" as the first token in the class declaration. Found in Dart 3.0.6 stable on Linux x64.