The mono homepage HAS CHANGED to http://www.mono-project.com.

Before the code listing there is

"Example 2-2 shows Hello.cs with the fully specified Hello.World
namespace [...]"

but the code is missing the following:

namespace Hello.World {
[...]
}

The first part of the example is missing a closing brace.

namespace OReilly {
namespace DevelopersNotebook {
public class HelloWorld {
...
}
}

should have an extra } at the end:

namespace OReilly {
namespace DevelopersNotebook {
public class HelloWorld {
...
}
}
}

There is no while loop in the code shown on page 37.

Note from the Author or Editor:
Page 39, paragraph 1 should read as follows:

Having handled all the events, we set the FileSystemWatcher's EnableRaisingEvents flag to true to start it. The Console.ReadLine() method will wait for the return key to be pressed on the console, allowing the program to handle events as they happen.

The text states that XmlSerializer uses the SerializableAttribute at determine how to
serialize an object to XML. This is incorrect. The last sentence of the paragraph
should read:

Instead, the serialization formatters in System.Runtime.Serialization use reflection
to look inside a serializable class and determine how to serialize it.

Also, on page 39, the second sentence of the last paragraph should be changed to the
following:

System.SerializableAttribute is one attribute that shows up quite often; it's used to
mark a class which can be serialized, which is necessary for remoting (see "Access
Remote Objects" in Chapter 7).

Syscall.chmod(file, (FileMode)0x777);
should be:
Syscall.chmod(file, (FileMode)0x1ff);

lower in the page;
...changes it permissions to 0x777 (rwxrwxrwx), full read....
should be:
...changes it permissions to 0x1ff (0777 octal), full read....

According to example 3-9, the following is wrong
"started on" and "at"
it should have been:
"on" and "started at"

Since writing the book, the name of the NUnit library has changed to
'nunit.framework', not 'NUnit.Framework'.

The new compile line should read:

$ mcs -target:library -r:nunit.framework MathTest.cs

The command
"xgettext -o monodn-intl.potMain.cs" is missing a space and should read
"xgettext -o monodn-intl.pot Main.cs"

The 3rd paragraph describes "runtime serialization" as a way to serialize an object,
possibly to a binary format, and "XML serialization", as a way to serialize an object
to an arbitrary XML format.

The 4th paragraph says:
"In this lab, we show you how to use runtime serialziation to serialize and object
instance to XML..."

This sentence has two issues:
1: The example uses XML serialization, not runtime serialization. The example uses
System.Xml.Serialization; runtime serialization would use
System.Runtime.Serialization.Formatters.Soap (binary and SOAP being the current
runtime serializers).

2: "...to serialize and object instance..." should to "...to serialize an object
instance...". That is, s/and/an/.

Note from the Author or Editor:
On page 192, paragraph 4 should read as follows:

In this lab, we show you how to use XML serialization to serialize an object instance to XML, and to deserialize XML back into an object instance.