BTW Book of Revelations + Battery + X-Ray Vision is where another exploit is at. Lets you use the Secret room as a base as you pop into an adjoining room to recharge, then get back to the Secret room without clearing the other one. Unlimited health right there, especially if you pick an easy second room (found one with my mirror twin, heh.)
You can also substitute Dr Fetus for the X-Rays.
Don't be scared of nightmares; make them be scared of you.