The crux is probably near the bottom, where getting up the corner and onto the face is just a little tricky. But it all seemed pretty much evenly 5.5 to me, unless you go too far right and try to get over the cave near the top. That is more challenging, and probably is off-route.
It's fun but short, and you can try different variations once you have the top rope set up. Just be aware of the pendulum if you climb far left of the anchors.
Find Layback, the open book at End Crags. Go left, around the corner, and you will find End Route, which starts in a corner where two cliff faces slope together. If you walk a little further on, you will see the Midstate Trail going up the cliff; so End Route goes up the rock face that borders the Midstate Trail. Hence another way to locate the route is to find the Midstate Trail and walk right of it.
Start in the corner, and climb straight up, trending just a little to the right of the face as you go up. Eventually you hit the top and you're done. You might want to try it several times, since the face is wide enough to do it various ways.
I found this route in Boston Rocks 2nd ed. (p. 53). Be aware that the drawing of the cliff face near the top of the route is not so accurate in the guide, so you have to figure it out as you go. When I climbed it with my partner, I believe we navigated too far right, and were unable to find our way over a 3-foot wide cave in the face. The rock above the cave has very thin holds, which makes it seem much harder than 5.5 at that area to me. We wound up going left to get around it, which I think is actually the correct way to do this route (i.e. go left of the cave, not over it). Someone please comment if you know the route better.
Top rope. Possibly it can be led, I don't know, I didn't try it.
There is a stout tree and a huge boulder a little to the right of the top of the route which can be used for anchors. I used about 30 feet of webbing, not doubled, to set 2 anchors.