There are quite a few topics about this, so if you want a range of sites or books you can check out some of those. I don't know anything about books regarding elvish languages, but if you do a search you'll come up with loads of good websites. You'll probably often hear the warning- stay away from the Grey Company. They kinda made up their own elvish.
I'd reccommend
Council of Elrond
You have to register, but then you can use their worksheets- which are marked by the mods, lessons, phrases etc.
Good luck.