These books have the prices for the tasks or jobs that you do. Each tech has a book and shows the customer the price for the task in the book. The customer is more likely to approve the price when it is shown to them in a book. The books make it easy for the techs to price the jobs.

Example: Customer wants you to come out and install a ceiling fan they just purchased.

The customer is informed of a service charge for a tech to come out and look at the job.

The tech arrives and removes the existing light fixture. He finds that the existing box is not rated for fan installations and there is only a swich leg in the box so he will need to get power from another source for the fan.

The tech opens the pricing book and shows the customer the price for the task of installing the ceiling fan and writes it on the invoice. He then shows the customer the price for replacing the box with a fan rated box and writes that on the invoice. Finally he shows the customer the price for running power to the fan and writes that on the invoice. He would then total up the 3 tasks for the total price.
The customer would then sign that they approve the price.
If the customer declines the price the tech would reinstall the light and collect the service fee and leave.

If the customer approves the price the tech would complete the work and then get another signature from the customer stating that the work was done to their satisfaction.

If the tech sees that the receptacles in the kitchen and bath are not GFCI then he would inform the customer of this and show them the price in the book to replace these with GFCI receptacles.

That is one of the purposes of the book is so that any tech can price the job or additional work on the spot. For your company to grow you need to have a system so that techs can price and sell the jobs. If you try to price all the jobs yourself you will be limited.