Not only is membership free for locals, it's free for ALL Maricopa County residents.
But that's not the best part - the BEST part of this branch (and the whole Chandler Library system in fact) is the selection of DVD's they have for check out. They have very recent releases as well as some oldie-but-goodies. So next time you want to an awesome movie, check out the Chandler Library system before you spend a whole dollar at Redbox.
They also have a great selection of CD's - from mainstream to somewhat obscure to pretty awesome "deluxe editions" (I found Rancid's 3 disc
edition of Let The Dominoes Fall at two of the branches).
The Sunset branch isn't huge but it's got LOTS of stuff, and if you don't want to trek to one of the other locations they'll transfer stuff for you.
TIP: check out the children's section's DVD's - I don't know why some things are over there instead of the regular section - but there can be some goodies over there.