The camera is not shaking the text, there is very little in your shot to track so at that part of the shot so the track is very unstable. The only thing the tracker has to look at at this part is the white wall and the out of focus book case. Most folks believe that if the Camera tracker gives you a solution you are done. That is almost never the case. Good Camera Tracking requires some careful observation and some hand work.
Open up the keyframes on your camera by pressing selecting the camera and pressing the U key. Select the position keyframes and then enable the graph editor. I'll bet you see a bunch of squiggly lines at that part of the track. Push in to the timeline so you can see the keyframes where position goes astray and start deleting as many as you can while still preserving motion. You might also want to try and apply the Smoother to the keyframes.
If this were my project I would split the clip just before the book comes into frame and Camera track only the end of the shot. This will eliminate superfluous tracking data from the camera solution and should give you a more stable track. Where the shot looses things to track and track points start jumping around delete as many trackers as you can (CC only). If you enlarge the track points to about 200% they will be easier to observe. The more stable your track points appear the better the camera solution. Then set the ground plane and origin, attach your solid or null and add a camera. Check the keyframes as described above and try and smooth out any remaining rough spots.
Thank you so much! I took your advice and it seemed to help a lot. However, there is still one little glitch that I can't quite figure out.
You can see it in the video on the link below, but the text "moves back" in the first few frames even though I already smoothed out the graph editor (see screen shot).
Here is a link to the video. It may be hard to notice, but you can see the text "jerk" right at the beginning.
I came so close to finishing, but can't seem to get this one last thing! Your help and expertise would be greatly appreciated. Please let me know if you need more clarification to answer.