Elvish dictionary

[Aiwendil]

If you want true Tolkien Elvish get the Languages of Tolkien's Middle-Earth by Ruth S. Noel.

Actually, Noel's book is not entirely accurate in many places (that's putting it nicely) and is generally considered inadvisable. The best resource for learning the Elvish languages is Ardalambion, mentioned above. If you want a real book, there's An Introduction to Elvish by Jim Allan (who used to post on these very boards); but unfortunately it's from prior to the publication of the Silmarillion material and is thus not comprehensive.

Quettaparma Quenyanna is a decent dictionary - it's certainly the longest English-Quenya that I've seen, though it does still omit a few words and it contains a small number of errors.