I think it's EMPIRE, following the titles of the other two, six letters, and begins with an "E"..

nup its brisingr
:p haha jokes

the funny thing is that when i started reading brisingr.... i actually thought it was the last book and when i started getting to the end i got suspicious if it would actually finish...........It will be called EMPIRE or ELDUNARI , i think......

i think it's awesome how the third book is named after the first spell
eragon used, AND... hng on. SPOILER ALERT, it's the name of eragon's new SWORD!

@luvmurtagh
The same thing happend to me and I was about 10 pages before the end and I thought: "WTF? When are they going to kill Galby?"