Somewhere in the lower left of the map with the severed heads on a stick, a book talks about secret stairs in the maze. Anyone find them?

It's possible that this is referencing an invisible ladder in the area with a portal and the torture device overgrown with grass (directly to the right after entering the maze through the "main entrance"). It's the top left area (assuming North is up).

The portal is only reachable by teleporting up to a plateau. However, in the bottom-left corner of the area (i.e. the corner with a hole in the wall), there's a pressure plate hidden between the plants. If you stand on that plate, a ladder to the plateau with the portal appears.

I'm not sure that this is what the book was referring to, as it's not all that spectactular (that said, it doesn't need to be) and a ladder isn't stairs.

[This whole post is a spoiler]
If you kill the void salamanders and head southeast from there rather than going NE to the Maze, you'll end up at that glowing cave entrance (Braccus's vault). Instead of entering the glowing cave, teleport across the water to continue east along the beach. As you make your way to the SE corner of the island there are a number of hard-to-spot vine ladders going up, the last of which bypasses the Gargoyle Maze entirely and takes you right into the tower.

Yes--to avoid the maze go around the back of the tower, counterclockwise from entrance--teleport across short water break.

Or get the braccus rex item in the vault, then walk to the door where you start the maze and talk to the skull that's on top of the door. showcase the item and he ports you straight in front of the tower.