If you're considering a Seven, or one of its successors, this book should be your first. The are many ways to go when one thinks about buying a Seven. Original? Successor? Clone kit? Scratchbuild? Ortenburger gives you an excellent survey of the possibilities.
To describe the original Seven, there is a succinct history that is focused on specification and engineering. Useful stuff if you wish to make an "historic" car build.
If you find you're keen on a turnkey car, or kit, I have to concur with the other reviewers. Very informative. You'll have enough information to see if you want to do it from scratch with Ortenburger's Locost survey section.
There's even a section on miniatures. I was surprised to find the Tamiya 1/12 Caterham superscale kit omitted though, since a few forums found building one useful for when they screwed together the real thing.
The appendices with the legal documents from Caterham's actions against other Sevenesque manufacturers is interesting, and more beneficial than you might think...
This is a wonderful book for anyone interested in the Lotus seven type cars. Dennis has done a great job in describing most (if not all) manufacturers of the seven copies. This is one of my favorite books with lots of great pictures. Highly recommended.