Holy cow, what an amazing follow up! I read this bad boy from start to finish in one day because I was so hooked! Head On is the follow up to Lock In which I adored a few years ago. I didn't give it a re-read before reading this and I thought I would be a little rusty on all the particulars but I was not. Win! John Scalzi continues to dazzle with his complex and brilliantly detailed worlds. This novel picks up not to long after Lock In, and follows FBI agents Chis Shane and Leslie Vann as they try to get to the bottom of an athlete's death. Hadens (or those with lock in syndrome) don't generally get to be star athletes due to their robot bodies (called threeps). However the sport of Hilketa involves violent matches with threeps so it's perfect for Hadens. Even though it's a violent sport, it's safe since those playing are really locked in, in their beds, but one day a player dies and it's up to Shane and Vann to get to the bottom of it and figure out if it was an accident or if there is something else sinister going on. Fascinating and fun, world building at its best! I can't wait for the next in the series!!!