Quest Objectives
Bring the Sin'dorei Tome of Summoning to Zevrost in Orgrimmar.
Provided: 
Sin'dorei Tome of Summoning
Description
You were wise to take this, ‹name›. More than killing Rimtori, keeping this out of the blood elves' hands will ensure they are powerless to retaliate against us.
As for deciphering the tome itself, I have a contact in Orgrimmar who dabbles in such things--a warlock named Zevrost. He can be found in the Cleft of Shadow.