Astronauts on most missions are allowed to bring personal items with them. Depending on what kind of mission, there are of course limits on mass and volume for their personal luggage. However, a paperback book would fit into the parameters of most missions. So an astronaut bringing a novel into space as a personal item is plausible.
However, the question is how this item would get into open space. Most missions avoid putting anything into orbit to avoid unnecessary space debris. Trash is usually collected and sent back to earth. The ISS uses the expendable Progress transport capsules for this purpose, which then burn up in the atmosphere. So the only way for a book to end up in orbit would be by accident.
It could happen that the book ends up in the airlock during an EVA and leaves the vessel this way. However, this would be quite a sign of negligence to have unexpected objects in an airlock. Using an airlock for an EVA is a very dangerous activity, so the airlock should be checked beforehand.
It could also happen due to a catastrophic accident on the vessel. A loss of cabin pressure through a large enough hole could cause some loose items to get blown into space. A collision with debris could cause this kind of damage. Such an event would also be likely to cause the destruction of the vessel and the demise of the crewmembers on board.
Regarding the book itself: In either case it would end up in an orbit very similar to that of the vessel which lost it. When that orbit is high enough to avoid atmospheric friction (the ISS orbit would not), it could stay there for a very long time as another piece of space debris. However, the strong sun radiation would likely cause the paper and ink to bleach, so it might not be readable anymore after a few decades.