Both are valid, and there is no "best`way. Notice that in the book method, you are left with an index finger free to add notes or to switch to on the nut-side of the chord. With the normal method, you have a pinky left on the bridge side for notes.

So, depending on what ad lib or embellishments you might do, one or the other fingering would be better. If you are alternating G & G7 for example, the pinky method would be easiest to use.

Also, consider what chord you might be moving from to the G or going to after the G. If it`s a fast chord change, it can be handy to already have your fingers ready on one side of the chord or another.

So it is situational as to which is best. I only play the pinky-on-the-E form if it is required for one reason or anther. Although I have known people that routinely play that way.