I got the Wrox.Beginning.JavaScript.3rd.Edition and wanted to start learning it from scratch, then my boss came along and said that why bother, learn jQuery. Can I understand jQ
If you already have an understanding of C#, you'll have a head start learning Javascript and it shouldn't be too hard to pick up. I'd stick with that Javascript book though, since you need to know Javascript to use jQuery. Once you are comfortable with Javascript, move on to learning jQuery. The jQuery docs are VERY helpful and can answer almost any question you have.
Good luck with learning it, it'll be worth it.
jQuery Docs