How to Root the HTC One E8 Method One

I. Before You Begin

1. This will void the warranty of your device. We won’t be held responsible if you end-up bricking or damaging your device. Do it at your own risk.

2. This should flash a custom recovery as well.

3. This should only work on Windows based PCs.

4. You should have appropriate drivers installed on your PC. If you haven’t, 

5. You must have unlocked the bootloader of your device. You can do so from the HTCDev website.

II. Downloading Required Files

1. Download ADB and save it to your desktop.

ADB

2. Download TWRP Recovery and save it to your desktop.

TWRP Recovery (Download link’s available in the first post)

3. Download SuperSU and save it to your desktop.

SuperSU (Download link’s given in the first post)

III. Flashing a Custom Recovery on the HTC One E8

1. Extract files from ADB to your desktop by right-clicking on it and selecting Extract here.

2. Enable USB debugging on your device by heading to Menu > Settings > Developer options > USB debugging.

3. Plug in your device to your PC via USB cable.

4. Launch a Command Prompt Window on your desktop. To do that, simply hold down Shift and right-click on any blank area on your screen and select Open command window here.

5. Type in following command into the Command Prompt Window:

adb reboot-bootloader

6. Your device should reboot into bootloader mode.

7. Then issue the following command replacing filename.img with the actual name of the recovery image you have downloaded:

fastboot flash recovery filename.img

8. It should flash the recovery on your device.

9. Then, issue the following commands:

fastboot erase cache
fastboot reboot

10. Your device should reboot.

11. You’re done!

Great! Your HTC One E8 now has a custom recovery installed on it. Here’s how you can root your device:

IV. Rooting the HTC One E8

1. Connect your device to your PC via USB cable.

2. Copy SuperSU from your desktop over to the root of your SD card.

3. Open a Command Prompt Window on your desktop. To do so, simply hold down Shift and right-click on any empty area on your screen and select Open command window here.

4. Type in following command into the Command Prompt Window:

adb reboot recovery

5. Your device should reboot into recovery mode.

6. Tap on Install.

7. Select the SuperSU .zip file to be flashed on your device.

8. Tap on Swipe to Confirm Flash.

9. It’ll start flashing the file on your device.

10. When it’s done, reboot your device by tapping Reboot followed by System.

11. You’re now rooted!

Congrats! You’ve successfully rooted your HTC One E8. Your device now has root as well as a custom recovery that’ll help you flash a custom ROM on your device.

Please have a look to Method Two , should be much easier ...:-)