[Jo flute player]

Hello
I've downloaded Callibre which was recommended for an ebook I had. Initially, the book read OK but the writing was a little small, so I tried to enlarge it (not knowing the platform well) and now all the words are jumbled up. I uninstalled it, and the ebook, restarted my laptop, reinstalled it and still the same jumbled words! Any advice gratefully received please. Thank you,
Jo