Reddit mentions of LPI Linux Essentials Certification All-in-One Exam Guide

Pick up Linux Essentials as a way to study and learn while you practice. Make several VM's on your current computer to practice with, try different distro's and different environments. By the time you're done with the book, you should understand the inter-workings of Linux well enough while having played around in VM's to decide which one you like best.

I for one, have a preference for OpenSUSE in KDE environment. I did not like Ubuntu or GNOME, and to each their own. The most vexing thing to change over, yet one of the greatest strengths of Linux after you're comfortable with it, is how modular the system can be.