Gyroscopic Investing

I purchased an book (related to watercolor painting).  It easily downloaded to my imac.  When I double click on it, it opens a new window with the file name.epub but it says "locked" and the window is blank. Is there really no way to read on imac or mac laptop?


Two points:  I'm still using mac OS 10.8.5 (though I could upgrade if it made any difference).
I do have an iphone, but want this on my computer, not the phone.

Thanks for your time.

Download iBooks. It's free. You can get it on the Mac App Store. I don't think you need to upgrade your OS, but if you do, that's free too.

If you don't like iBooks or don't have or want an Apple ID and therefore can't use the Mac App Store, Calibre is a free-open source epub reader that will also do it.

Thanks PS. Calibre worked great.