Download and install one of the many free sound recording programs like Audacity or the Free Sound Recorder found here: http://download.CNET.com/Free-Sound-Recorder/3000-2168_4-10698910.html
Connect your microphone to your computer's microphone input. Use a good quality microphone for good sound quality.
Record yourself or someone else reading your book while using your recording software. Separate the recordings into chapters with a different file for each chapter. This will allow you to find a specific point in the book without having to fast forward or rewind through the entire book.
Save all of your files to your hard drive in MP3 format. This will conserve space on your computer and allow you to fit more of your book on one CD. Save all of your book's files, in a folder with your book's title, in your Music folder. This will allow you to locate them easily when preparing to burn them to disk.
Software may vary. If you can burn the files to disk using your sound recording software, consult the instructions that accompany your software for guidance. If your sound recorder just records the files but doesn't burn them to disk, save all of the files in your music folder and use your media player to burn the MP3 files to disk.
Select all of the files in your book's folder and burn them to a CD using your recording software or media player.