Peeing

According to comments on the wiki, "Everything is Terrible" makes alternate colored monsters and bosses more common. This is actually good, because alternate colored monsters tend to leave drops on kill.

According to the mechanics guide, it also makes Curses more common in Wrath of the Lamb.

Additionally, however, bosses drop one less heart pickup (heart, half-heart, spirit heart) than they previously did.

According to the wiki, the only item that seems to be able to raise your stats above the maximum is The Sad Onion, which doubles the firing rate no matter its current value. I have very little personal experience with that item, so I can't confirm or deny this.

The stat that I find easiest to max out is damage, as I've often managed to get quite a few damage enhancing items in a single run (which would have put me over the maximum looking at the bars in the pause screen). I always seemed to hit the same cap, no matter how many damage enhancers I picked up.

In light of the above, my previous version of this answer indeed states that the item is useless once damage has been maxed. Further research, however, proves that I was mistaken. To test this, I played with Judas, picking up both The Pact and Pentagram, which maxed out my damage. I then engaged the boss Gish. Here is Gish's health-bar before I started measuring damage:

I then shot Gish three times, bringing him down to this:

The difference was 11 pixels. Then, I used the Book of Beliel and shot him three more times:

This time, the difference was 15 pixels.

So as a matter of fact, the Book of Beliel can and will take you above max damage.

Sadly, this experiment doesn't give a single conclusion about the multitude of other ways that one may try to raise his stats past the maximum, but strictly speaking, the answer to your question is yes.