On The new HTC One (M8) you can change the font style without rooting it with the option to access to so many font styles available to install from Google Play Store. To change the default font on HTC One M8 do as follows:
1. Open Settings application
2. Under Phone settings, open the Display & Gestures.
3. Under Display settings, open the Font Style.
4. Now you can use either the available font packs or get some new ones from Google Play Store by touching the "Get Fonts Online" option.