Were these books given to owners of the Lotus version, or did they have to buy them?
They weren't but they are numbered as per the vehicles although the book ran to the full production run unlike the car itself (more books than cars). I did start to try & find the matching book number to my car but a fruitless search.
I paid circa. £130 for mine over 2 years back but have noticed the sell price going up lately (not that I'm selling). It tells the story from the original concept of the Lotus Senator with drawings & mock ups of it through to the build of the LC/LO & as Pete said, cutaways, schematics, tech spec et al.