Start with Learn Astrology by Gauri Shankar Kapoor and Astrology of the Seers by David Frawley and then gradually pick up other authors.
The basic difference is in North Indian Horoscope the Houses are Fixed, while in South Indian Horoscope the Rashi are fixed. It can get a little confusing but then both have their own advantages. Actually south Indian chart is more emphasis is given to Nakshtra, therefore they fix the rashi and Nakshtra and house keeps chanding. Therefore it is difficult for a new person especially with North Indian astrology background to catch the Ascendant as it keep changing. Where as in North Indian you know the Ascendant is fixed.