I've bought Blood and Space and done a first pass reading. Here's a short review:
Blood and Space: Rating 3/5
Blood and space is a relativly generic Space supplement for D20. Using D20 modern (or T20 or Dragonstar) you can add space ships, space combat and a variety of equipment. Included are additional classes, feats, and skills to use the proper equipment.
The classes are interesting, if generic. I'm not an expert on D20 class balance, but I noticed a few odd thing about them (The doctor has d4 hit dice and 6 SP per level, but the scientist has d6 hit dice and 8 SP per level?). If you don't like the generic nature of the T20 classes, the BS classes may be more to your taste. The Prestige classes are less useful (why three Marine prestige classes?).
The skills are all pretty obvious, and oriented toward the usual D20 combat items. The feats are the first place where I have problems. Some of the feats are obvious and ok (Item creation for armor, spaceships, etc). Many of the Piloting feats (barrel roll, gravity sling shot, wingman, Yaw and lightem(?)) look more like they simply should be included in the starship combat section as possible manuvers.
Equipment comes with 24 personal weapons, and the first of the really cringe worthy statements. The 9mm caseless gun requires oxygen to fire? Guns today don't require oxygen to fire, and never have. There's some armor, including powered armor and an orbital insertion suit (shades of Starship Troopers). Nothing exciting, but all useful.
There is a two page Trade system, but it's overwhemingly balanced toward losing money. There is a half page list of trade goods which can be used as examples for trading.
Starship construction is a five step process, and the book contains 26 pages of components to put in your ship. Step 1 is the hull, and there is a table of 25 predetermined hull sizes. The ratio between hull size and the amount it can carry seems odd. The smallest ships are 3.5 dtons (in T20 terms), can carry a single person. The largest ships are more than 3 million dtons, but only carry a crew of 400, 200 passengers and 100 tons of cargo?
The Hard-Science drives throw around a good deal of technobabble, but I understand the theory of starship engines and these make me go ewww. The second really cringe worthy part is the author either don't understand or don't bother to explain the difference between acceleration and velocity. There are four types of FTL drives and the book suggests selecting one type for your campaign.
The defenses add either armor (Ablative DR) or Shields (Regenerative DR) to the ship. Again more technobabble. Weapons continue the same. A few interesting ideas to add detail to the T20 weapon descriptions. There are some odd choices for the split between Hard Science and Space opera though. For example, if the Positron Gamma Ray Laser is a Hard Science weapon, why is the Gamma Cannon a space opera weapon?
Computers can be constructed to order, and much more simply than the T20 construction system. There is a good set of additional facilities you can add to customize your ship (Passenger cabins, entertainment facilities, troop transport spaces for troops or armor, and so on). Starships end up being about 3 orders of magnitude cheaper than the T20 equivelents (10s of Kcr rather than 10s of Mcr).
There is a neat system for ranking ships crews (other than the PCs) in terms of skills, and a short experience system to allow them to get better. If you have ships with more crew than just the PCs, this may be interesting system to take a look at.
Combat. There is an abstract system for doing ship boarding actions, rolling a single opposed skill check (plus skill mods), with the loser losing levels of skill through either morale or combat losses based upon the difference in the roll. Much quicker than a full fleged round by round D20 combat between 20 to 50 opponents.
Starship combat is basically aircraft dogfighting from Star Wars, not the realistic spin and accelerate from Babylon 5. Sensor ranges vastly outrange all weapons, but are still patheticly short ranged (160,000 miles max range on sensors?). Still combat is D20 simple, roll to hit, roll damage, subtract DR for armor and shields, apply HP to ship. There is a optional system for damaging internal components. Just to make things interesting, there is a variety of "Terrain" for ships to fly in, around, and through ranging from moons, planets and comets to black holes and cosmic strings.
The book completes with a collection of four pirate ships, two survey vessels, a cargo hauler and a light warship.
Conclusion: The art work is passable. The story (about a page at the beginning of each chapter) is a waste of space. I found the Crew quality section a good addition to my T20 rules. The rest is not very useful. If you dislike the T20 rules for one reason or another, you may find something you like here.