Two books that I just finished recently had very similar themes, but were definitely different in the details.
Both of these books however, involved having someone else in the main character's head. Confused? Let me explain.
The first novel, "The Lives of Tao" by Wesley Chu, was a book that I randomly picked up at the recent Book Expo in New York last week. It was a small hardcover book and to be honest, I figured that it would easily go into my suitcase along with the other books I was bringing home, and that is the main reason that I snagged it in the first place.

Tao is part of an alien race, called the Quasing, that unfortunately crash landed thousands of years ago on Earth, and their goal is to try to someday get off-planet and return home. What kind of alien is Tao and his race? Think Invasion of the Body Snatchers here, but not quite as dramatic. While the Quasing do have to attach themselves to host bodies here on Earth, it is a symbiotic relationship between them and humankind for the most part. They have the ability to interact with their hosts while in their bodies, and the ability to control some of their functions. They can hear every thought their human host has, and can see/hear/sense what they see, but can't control what they actually do physically unless asleep. Unfortunately for Tao, his most recent human host, Edward, is killed in the first chapter of the novel, and Tao is forced to join with the nearest available host or face permanent "dissolving", and the new host is not an ideal specimen of the human race. Roen is an overweight, aging, unsatistifed with life IT technician. Tao has no choice but to make him his new host , and Roen soon learns that he is not alone in his head. The Quasing split into two factions centuries before, Tao's faction, the Prophus, the other faction being the Genjix, and the two factions certainly don't get along. Tao has no choice but to attempt to educate and train Roen to the Prophus cause, as the Genjix are after Tao, and thus after Roen. His training begins almost immediately, from excercise to weapons training. Tao educates Roen along the way, and explains how he has influenced humanity from his previous symbiotic hosts throughout history. Genghis Khan anyone?
Roen has no choice but to become active in the battle against the Genjix, and it all comes to a showdown when the Genjix capture a love interest of Roen's, Jill. Roen, with Tao's help, manages to win a major battle with the Genjix, and as a result, the Genjix are forced to retreat and regroup.
The novel was at times humorous, but not quite laugh-out-loud for me. It did make me think about how much of our world's history could be a result of alien influence, but it took me about half way through reading it to really get into the story. There is a second novel out, The Deaths of Tao, and it will be interesting to see what Roen and Tao get up to in the future.
The Lives of Tao, Wesley Chu. Angry Robot. 2013. Isbn 978-0-606-35350-2
The second book involving people in your head was by W. Bruce Cameron, The Midnight Plan of the Repo Man. No alien life forms here, just the deceased type. Ruddy McCann is a repo man in Michigan who begins to hear a voice talking to him. At first he is convinced he has "Repo Madness" but it turns out this voice in his head belongs to Alan Lottner, who was murdered in a nearby town eight years ago. Neither one is sure why they are able to talk to each other at first, but Ruddy realizes that the circumstances of Alan's murder matches a vivid dream he recently had. Alan can see and hear everything that Ruddy does, but can't hear his thoughts, causing Ruddy to have to keep quiet his conversations with Alan lest his friends and family think he is going crazy. To make it even more interesting, Ruddy also realizes that the girl he helped on the side of the road when her car broke down is Alan's daughter. Try going on a date with a girl when her father is in your head yelling at you to leave her alone! Ruddy starts looking into the circumstances of Alan's murder, trying to figure out why he is in Ruddy's head, and learns what happened, getting into trouble with the local police along the way when suspicion turns towards him as a suspect in the unsolved case. Adding into the mix is assorted characters in Ruddy's life, his sister struggling to save the family's bar, a naive friend Jimmy who keeps cashing mysterious checks that bounce at the bank, to Kermit, his boss's nephew who winds up getting Ruddy into predicaments during repo's. The novel's character of Einstein Croft, ingenious in keeping Ruddy from being able to repo his truck, along with toting a rifle and keeping a goose as an intruder alert at home, is an added bonus.
Eventually, Ruddy starts to figure out the circumstances of Alan's murder, while getting arrested, polygraphed, shot at, and almost drowned in the process. Alan helps to solve the mystery as well, along with making Ruddy get back into shape by running and working out at night during his sleep, as well as cleaning his bachelor pad and making Ruddy think that his sister did it for him. Add in a subplot of his sister's plan to save the bar business by teaming up with Kermit to use the bar's credit card machine to swipe and charge customers for a pay-for-phone-sex line, and this novel is an entertaining read. I was able to learn some tricks that repo-men use, as well as some tricks to stop repo-men from being able to take possession of a vehicle in the middle of the night. An enjoyable read, with plenty of laugh-out-loud funny parts.
The Midnight Plan of the Repo Man, W. Bruce Cameron, Forge. Oct 2014. Isbn 978-0-7653-7748-7