I would appreciate a short, single-paragraph description regarding the "Blood and" series. . . please and thank you. Multiple perspectives would be good too.
The "Blood and" series is a collection of d20 Modern add-ons. Each tweaks the base rule set with new feats, talents, skill uses, equipment, and Advanced and Prestige classes. A couple of them also have new base classes.
Personally, I've found them a mixed bag.
Minuses: Chuck's dedication to realism has lead to some things that are hugely important in real life being translated into game mechanics, when the looseness of the d20 system intentionally glosses over many of those points. Some of his feats are obviously better than the core rules, others are worse. Similarly, the skill uses and talents often leave me wondering "why did he even make mechanics for that!?"
Pluses: They're built with love; as screwy as some of the stuff has been, it's obvious that Chuck really likes and groks the base rules. They are very focused supplements, but they all are designed with an eye towards combining (most of) them into a massive and sprawling whole, so there's a lot of good balance between them and even the occasional cross reference in the campaign options. Lots of great research, ideas, and flavor text, all done with skill (and often references), compiled into one tasty bundle. Excellent product support, in the form of free updates (or good coupons when they completely re-publish the book), and the unique opportunity to discuss the material directly with the author (you're a good man, Vigilance).
I pick up the Blood supplements for all their non-mechanical stuff. That's me. Others find the mechanics to be semi-divine in their appropriateness and balance.