Hi noobpianist90,
Your first impression was right. You should shelve that book because what's printed in that passage is confusing and wrong.
A much better book is Mark Levine's Jazz Piano Book (which is pretty much the jazz piano bible).
C blues is indeed derived from C minor pentatonic. C minor pentatonic is:
C Eb F G Bb (repeat 8va...)
C blues adds a flattened 5th and is therefore:
C Eb F Gb G Bb (repeat...)
What's cool is that you can re-purpose this formula to play licks in relative Major keys. Say you are in C major (doing a Boogie-Woogie piece in C Major). You can now employ the Major Blues scale (which is of course this time is derived from the Major pentatonic).
C Major pentatonic: C D E G A
C Major blues: C D Eb E G A
This time as you can see, you add a flattened 3rd to the mix. This will sound good over a C major chord, especially C7. Good players will mix the two. For example, use the minor blues scale the first time through the tune, and then the next time around the form, use Major blues - mix it up.
Let's do a minor blues scale in A:
A C D Eb E G
Wait a minute, those are the same notes as the C Major Blues, just starting on a different note! That's what I meant about re-using the same scale formula for relative minor-Major keys. So the above works for C Major as well as A minor. If they share the same key signature, you can re-purpose the same blues-scale for both. Buy one, get one free!
Good luck in your blues endeavors.
-Erich