Consider using simple infographics - see "The nouns project" #14
Description
The nouns project has simple infographic icons for everything. I started using it this year and it has helped so much.
It's creative commons and says "When using it for any project, you are required to give credit to the icon‘s creator or purchase a royalty–free license." You can use any icon with no watermark if you apply for their education level which I think is $20/yr.
A few sprinkled in the book might help break up the text. Like even searching for "launch" has some cool images of spaceships launching from screens/computers.
https://thenounproject.com/search/?q=launch