"The Vision"...I can't remember the author....and "The Battle is Not Yours" - Yolanda Adams.
I use a lot of super-imposed chords (as DDW4E put it). The most I'll do is a 9th, in my right, but if you add it to the left hand, it'll make 11ths and 13ths a lot of the times.
C-E-G-B / D-F#-A-D (a DMaj over a CMaj7 = CMaj13)
C-E-Bb / Eb-Ab-C (a AbMaj over a C7 = "C7 #9#13")
Just practice doing diatonic chords. It's easier to do it in the key of C. Start on C then build your chord, and move it up diatonically, until you get to the next C. Do this with chords with 3 to 7 notes. Once you have those memorized, you can use them, by applying them to your progressions.