Blood is not a revolutionary game. But it did have the most unusual plot I have ever seen in a FPS. Let me start with level design, for you traverse many real-world locations I have yet to see duplicated in any other FPS. The weapon selection is better than in any other FPS ever made, for where else could you use an aerosol can or flare gun to set your enemies on fire and watch them scream, "It burns!" The enemies are also memorable, for you have cultists which shout Latin-Sanskrit phrases at you (which have real English translations), and zombies who emerge from the ground and say "More Brains." The graphics, while considered poor by today's standards, (though I like them) do add a certain atmosphere to the game. Also, the one-liners from Caleb, Blood's protagonist, are what set it apart from others of the same genre.
The bosses are to easy to defeat. Shial is quite scary though. The violence in Blood is intense, so if you do not like violent video games stay away from this one.
The Bottom Line
One of the best FPS around. Much better than Duke Nukem 3-D. Find and play it, you are sure to have one of the best experiences ever in computer gaming.