Meant to be a disturbingly good game, could be worth the dollar and a bit to try it out.
Rundown of deals: (75%-76% off)
Binding of Issac - $1.24
Binding of Issac + Soundtrack - $1.49 (buy separately to save 1 cent)
Binding of Issac Expansion: Wrath of the Lamb - $0.74
Soundtrack - $0.24
Best deal is to buy them all separately, total cost would be $2.22 for the lot.
Metacritic gave it an 84/100! (in case you wanted more incentive to get it)
It seems that Steam is needed to play the soundtrack if purchased from the deal above.
You can also buy the soundtrack from Bandcamp for US$0.99 (or more if you're generous), Paypal is accepted. You can choose from Flac, 320k MP3, AAC, Alac, Ogg formats. Steam not needed!
http://dbsoundworks.bandcamp.com/album/the-binding-of-isaac-…
Try tracks 11 and 3 if you haven't heard the music before.