[...]<br>It was very difficult to grasp in Latin (I've had a try on it), not that much easy in the Motte facsimile translation (I can assure it), and the Cajori-Motte edition was only half modernized and otherwise flawed.<br><br>This edition, sponsored by I.B. Cohen (the Latin editor) gives us a fresh, modern English translation of the text, and -almost as thick- a guide to using and reading this all-important book, which is not -as everybody is aware- an easy reader. One word of caution: Newton was, of course (pace Leibnitz), the discoverer of calculus, but he doesn't use it here, but "more geometrico" rigorous proofs, much in the style of that other genius of all ages, Archimedes. If you need help grasping the contents and impact of this work, then you must get some book like DENSMORE, D., Newton's Principia: The Central Argument (other auxiliary books are commented in the Guide potion of the book I'm reviewing).