If Urushihara's previous "Venus" artbook couldn't satisfy your love for semi-clothed females, then "Sigma," this 2006 release, will serve as a nice backup plan.
Sigma contains artwork from Urushihara's most well-known franchises (Plastic Little, Lemnear, and so forth) but most of the collection is devoted to his own creations, and features some beautifully-painted and airbrushed illustrations of the female form. Once again, if images of multiple girls or large breasts are your thing, then Urushihara's your man. A very few images are duplicated from previous books (ex. an image of Street Fighter II's Chun Li), but it's nearly all new content.
Also included is a black and white comic unique to this volume entitled "R.C. Twins". It's short, but it serves as a perfect example of how well the artist understands the use of halftones and semitones in a book to produce the desired effects. Ebil Panda's gallery even includes the author comments, questionaire and index from the back of the book, so you're getting the whole deal. There's no torrent download option, but that shouldn't keep you from wearing out your right-mouse button; the whole thing's a keeper and deserves every one of its five stars that it currently enjoys.
So go wild - it's bigger than Venus, longer than Venus, with 99% new artwork. What on earth are you waiting for? These things aren't going to download themselves.