This book covers basic maintenance skills that can save your community hundreds of dollars and berakhot levatalah. Ideally, you would learn this material in conjunction with a teacher; a real sofer's apprenticeship lasts several years.
A sofer's apprenticeship takes years because there is so much halakha to learn. If you have not learned the halakha, you MUST work under the supervision of someone who has, or you WILL pasul your Torah.
You can quite easily make a sefer pasul by doing the wrong thing. Adding to letters or erasing from letters in the wrong ways can look fine, but be absolutely pasul. This is bad.
However, with this book you can learn to prevent some of the more avoidable problems, and help solve some of the easier problems. You'll also learn about avoiding more complex problems.