Aloha!  Welcome to my humble online abode!  This is the home of the world-famous* textbook, On Beyond Euclid.  

This  curious  little  book  is  basically  a  hitchhiker’s  guide  to  Book  I  of  Euclid’s Elements.   We  travel through each of the forty-eight Propositions—more or less in order—and see how each one generalizes (or does  not  generalize)  to  hyperbolic  and  other  non-Euclidean  spaces, including Einstein's special theory of relativity.    The  prerequisite  is  high-school (circular) trigonometry.

The whole darn book is available for free as downloadable pdf files, although it's copyright ©2005 by Ben Jacobs.  Creative Commons rules apply: Creative Commons License.   This website contains the  newest edition, which is being continually updated, revised, and (hopefully) improved.   The first edition paperback might still available in print on Amazon; I won't bother including the link!  Finally, the cover art above is by Hannah Jacobs.