While Red Mars was a strong stand-alone novel about the first settlers of the Red Planet, Green Mars and Blue Mars really need to be read together. For example, several of the main characters who took up so much space in Green Mars without actually contributing anything finally find significance in Blue Mars. There are also strong continuities of plot and theme, especially in the way that the second half of Green flows into the first half of Blue. While Green took forever to get going, Blue starts considerably stronger before fading into Robinson�s now-familiar descriptions of Martian scenery that can be described as either breath-taking or interminable depending on your point of view. In fact, the greatest weakness of Blue is that feeling that we�ve seen it all before. After the thousand-odd pages that make up the first two volumes, readers might be hungry for some variety, a few surprise plot twists, a technical tour-de-force of some kind, but instead it�s pretty much business as usual on Mars, with the same (now aged) characters often grinding the same metaphorical axes. The murder mystery and sexual tension that drove Red has completely dissipated, and Robinson�s attempts along these lines in Blue seem spurious, if not downright silly. Readers who loved Green as much as Red will surely find this book rewarding enough, but those who didn�t feel Green was quite up to snuff won�t find anything special in Blue.