Hahaha I loved the humor displayed on page 20. Looks like you're sticking well to your idea of trying to make the book enjoyable and easy to read!

That’s my personal opinion but I prefer when line spacing isn’t so massive to stretch the page count. I’d rather have smaller line spacing with less pages overall than thinking I’m getting a 120 pages book only to find out each page only has ten lines.

Congratulations on the book but the formatting is very poor for a technical book. 10 words per line is good for a small paperback sized novel not for a technical publication. The excessive white space, the line spacing are also inappropriate. The most important element (arguably) - the equation also is the hardest to read due to the small size and how compactly it was formatted. If you've paid for the formatting as a service I'd try to get a refund and give it to someone more competent.