http://www.sec.gov/Archives/edgar/data/1490281/000104746911008605/a2205238zs-1a.htm
Bloomberg Businessweek has a good analysis of the pricing and valuation here:
http://www.businessweek.com/ap/financialnews/D9QGLA6O0.htm
See the Groupon IPO roadshow presentation here:
http://www.retailroadshow.com/sys/launch.asp?qv=7519056762608856&k=61094248141
And see a tongue in cheek, slide by slide commentary of the IPO roadshow here:
http://jackp27.blogspot.com/
A critical look at Groupon's revenue growth:
http://blog.yipit.com/2011/10/21/the-chart-that-will-scare-away-many-groupon-investors/