Ive read several books saying this is the fear week. Is this true?

There is a period during a pups early development which can occur any time from the 8th to the 12th week depending on the breed, a new puppy owner needs to be aware of the potential of anything really distressing happening during this time, if not handled correctly, impacting on the pup for the rest of its life.  The fear period is natures way of keeping a pup safe during the time when it gets more adventurous.