The Ringworld Engineers

Lots of inter-species sex in the sequel to Ringworld; nothing graphic, mind you, but it seems like you can't get though a chapter without somebody either having or talking about having sex. The mechanics of the Ringworld are fleshed out more which is fun and the identity of the Ringworld builders themselves are revealed. All good fun but this one lacked some of the awe of the first book and too many of the supporting characters come off as flat and lifeless. It makes me skeptical of the rest of the series but I know I'll probably end up reading them anyway.