I really like this book. I studied Euclid many years ago and decided recently to go through the Elements again, and I now often prefer my ipad to a paper book, especially when traveling. For me, the Elements are to math what Bach cello suites are to music. Both are simple, elegant, and examples of the best things in life. I was initially skeptical that this ebook would be a complete redo, but it is the same wonderful Sir Thomas Heath translation that I read in paper years ago. The interactive diagrams of the propositions are great! They bring it to life on an iPad and, for me at least, add extra insight into the proofs. My only tiny complaint is that many of the proofs extend beyond one page, and it is a bit of a pain to go back and forth to the diagram on the first page. Maybe there is a feature to change the font and layout, but I haven't found it. Another fix might be to reproduce the figure, perhaps smaller, on all subsequent pages of a proof. I suppose this could be a button that could turn these on or off. I hope that the authors are working on the rest of the books. Right now it stops at 4. I'm sure I will be eager to have more!