You are right dream interpretation is personal. Dream books can only guide you in the right direction and give you a general interpretation. Symbols do have a universal significance, for instance, dreaming of a house usually denotes the dreamers body, the place were we live and as most people live in houses that symbology is similar for everyone. However your personal experiences in life effect your symbology, a dog may mean loyalty, friendship etc but if were attacked by a dog previously then your dream meaning maybe completely different and may signify fear, danger, pain etc.
Love and Light, Splashcat