It's a book on perspective

>>2374272

Mechanical things? It's used for >everything<

Not that much but it definitely changes the way you think about space when you draw, do the exercises

>>2374272
Well, it's still useful, but if you don't intend to do industrial design or architecture, you can spend your time more wisely and learn perspective much more effectively. The biggest problem most rookies seem to have when getting comfortable with perspective is that they get overwhelmed and discouraged because they don't see it as a simple tool to create the illusion of 3D space on a 2D surface, but as a bunch of formal, complicated rules where everything needs to be carefully constructed.

It is much more effective to just read up on the basics, understand WHY we use perspective and then draw from life, using curvelinear perspective while always being conscious of your eyelevel and cone of vision.

I'd say it only becomes useful once you have an intuitive understanding of space anyway. After that it's a pretty cool thing to have though.

Even if you're not interested in "mechanical things", this is a very good book on Perspective. You can use the same methods in the book drawing organic figures.