I recently picked up a copy of Mongoose Publishing's
Macho Women with Guns d20, originally published back in 2003.
I got this mostly on a lark, having spotted a relatively cheap copy online (i.e. less than half of what bookfinder.com said it usually went for) and deciding to grab it. Even then, that was largely because there's no (legal) way to acquire the PDF anymore. There
used to be; I found remnants of a DriveThruRPG sales page (since even after a DTRPG sales page is shuttered, reviews posted for that product still remain), but it's no longer available digitally that I can find. Whether Mongoose decided to pull the book from digital distribution or they had to eventually cease selling it as part of their deal with the original publisher (that being Greg Porter of the Blacksburg Tactical Research Centre, aka BTRC).
Either way, I have a copy now, and having read it through it's not bad...relatively speaking.
Given that this book doesn't take itself seriously (the title should have been a giveaway, there) it's hard to level too many critiques at the contents in terms of taste. However, one of the most salient points that I've heard leveled at this book is that the d20 System's intricate mechanical presentation runs counter to the "don't take it seriously" tenor of the subject matter. This book is satire to the point of being farce, but at the same time has pages and pages of game mechanics for how things work.
To give one of the less-smutty examples of this, one of the vehicles presented in this book is a "combat unicycle," complete with not only a description but also an entry on a table identifying its top speed, hardness, hit points, initiative modifier, etc.
Personally, I see this as a feature rather than a bug. To me, the d20 System (by which I mean D&D 3.X, d20 Modern, PF1, and some near-identical stand-alone RPGs) are essentially the same game, and the incredibly vast array of third-party products lends itself to a "remix culture" that's incredibly diverse. The more material you have to work with, the more bespoke you can make your campaign world, pulling from many,
many different books in order to make your campaign setting's uniqueness show through not just in presentation, but in mechanics as well. Or in other words, I judge things by their cherry-picking potential, and so to me even a small amount of inspirational material justifies everything else in a given book. Combat unicycles alone make
Macho Women with Guns d20 a worthwhile purchase, in my eyes.
But I can understand that other people see it differently, and judge this book for what it is unto itself rather than what it brings to the d20 community as a whole. And in that regard, I'll admit some sympathy to the idea that working hard (i.e. playing a rules-heavy RPG) to play a game whose subject matter is inherently unable to take itself seriously can seem counter-intuitive. Most people aren't going to open a brewery with an attached bakery if they want to enjoy some beer 'n' pretzels.
And of course, there's a lot of illustrations of hot chicks in skimpy clothing here also, which I've heard is a point of contention for some people.