Once you enter the Grand Chapterhouse you want to turn right, here you will run into the Guardians of the Chapterhouse, you can take them out but they will rise again after a short time. Use your defensive magic and run past them, try to steer clear unless you absolutely have to. Next you will see a note in a spiked cage up on a pedestal. You will have to use some timing to get in the cage and grab the note.

Once you enter the next chamber you will have to dodge the fireballs that come out of the lion heads. On the far side of the two doors you will see one of the four books you need. When you reach it you will find the switch to open the doors here. Grab the book and the traps and Guardians in the area will shut down.

Go into the next chamber and hit the switch. You will want to keep up your healing magic and run through the Guardians and grab the books in the other chambers. After you grab each one the traps will also deactivate.

Sprint to the last book and grab it then head back to the pedestal where you found the parchment. Now head up the stairs and open the bookshelf.

This will cause the Causeway to open up. Odo will now come and he will advise you to visit the Meisters who are the cities rulers.