What happens if you use the 'you are special' book when all of your stats are at 10 or higher? I saw a question asking about the highest level you could get your stats to, but this specific condition was never addressed. Does it do nothing? Raise your skills higher than 10 or 11? I've already messed this up, and seeing as I have the ps4 version it would probably be faster for someone else to test this on the pc rather than starting my character over without touching the book.
It won't raise a SPECIAL stat that is allready 10 or 11.
However, (allegedly, I have not tried this myself) you can temporarily lower a stat with chems (such as Daytripper for Strength), use the book and then have 12 points total (source).
The "You are Special" book will not raise your attributes beyond 10.
However, any of the SPECIAL increasing Bobbleheads will, if used on a stat that is already at 10.