Suggestions

[Angrboda]

Daniel Dennett's "Elbow Room: The Varieties of Free Will Worth Wanting" is excellent.

I just happened across "The Oxford Handbook of Free Will" on Amazon and was impressed enough by the reviews to order a copy; I can't personally vouch for it and it will be a while before I get around to reading it, but if you'd like, when it arrives I'll give you an ignoramus' superficial appraisal.

Oh, and one thing to keep in mind is the distinction between compatibilists (who believe that free will and determinism are compatible -- that the two don't conflict) and non-compatibilists (who believe it's either / or -- that you can't have both); it's not always clear where a person falls on this issue solely from whether they advocate "free will" or "determinism". Perhaps Wikipedia or the Stanford Encyclopedia of Philosophy (online) might explain the issue better than my quick gloss.