I read this AFTER book 2 - The year of the flood. I think I enjoyed Flood better though I note that most people read Oryx first and preferred that... 
 Both books have the same style of present/past narration and the slow reveal of events leading up the Flood. It was interesting to see the events from the 'inside' and to see a different side of both Jimmy/Snowman and Crake, though I think Flood was harder hitting for me. Perhaps because it was my first experience with the craptastic imagined world and all the awful things that happen, but also maybe because Flood is told from the point of view of ordinary people living the hard life in the pleeblands. I liked that they didn't know all the answers, the whys/hows but were just faced with surviving the world post-outbreak with all its hardships and unanswered questions. In Oryx there was quite a lot of focus on society's desensitization to violence and sex, and the degradation of humanitarian ideals. In Flood these things also appear but are not so glorified perhaps. I dont know. I found the life in the pleeblands more interesting and shocking than life in the compounds with their noodie news and 24/7 access to live executions and kiddy porn. I understand the point that was being made but it felt a little overdone at times. 
 As for my review for Flood - I don't think I particularly missed anything reading them out of order, they really do run concurrently. Both are excellent speculative fiction and I am eagerly awaiting the publishing of the third instalment in September.