Established mathematics do not change much over time, though the notations and nomenclature often evolve slightly, especially at the most advanced levels. Teach Yourself Geometry, though published in 1948, is still relevant today.
Most of the book is formal definitions and theorems pertaining to various constructs such as parallel lines and quadrilaterals. Each section has a handful of appropriate exercises for the reader to try, with solutions in the back. The last third of the book is Formal Geometry, or the "proofs" that high school students everywhere dread.
I noted a few differences that I did not see compared to my modern (90's era) education:
- This book discusses bearing and cardinal directions, something likely more useful in the 50's than today. - It typically refers to 180° as "two right angles" rather than 180° - There are step-by-step instructions on how to precisely draw the various figures, likely useful for hand-drafting in an era before computer aided design. - They call trapezoids "trapeziums". I think this might be a result of being published in London.
If you master this book, you will have a solid grasp of geometry.