We often refer to Indian Astrology (Vedic or Jyotish) as if it were a monolith. But just as in Western astrology, there are mutltiple schools of thought. The predominant form of astrology practiced in India and is the most prevalent form by far that is practiced in the United States is PARASARI Astrology.
The major text in this tradition is the Brihat Parasara Hora Sastra which is considered the Bible of Vedic Astrology. The Brihat Parasara Hora Sastra is an encyclopedic collection of astrological techniques, many of which are only sparsely used or investigated by many contemporary astrologers. The other major reference texts in this tradition are Phaladeepika by Mantreswara; the Brihat Jataka (a curious collection which seems very much influenced by Greek astrology) by Varaha Mihira; the Jataka Parijata (a compendium of collected knowledge from various sources); the Uttara Kalamrita (a much later text, but clearly derived from earlier works) by Kalidas -- a little gem of astrological knowledge which contains a wealth of astrological gems; and the Saravali (a medieval text).
These texts are the backbone of Jyotish. The problem with many of these texts is that the translations of many of these texts have been relatively disorganized -- many astrology students have found the experience of approaching these texts very daunting because the techniques are often presented in a very random fashion. In my opinion, it is extremely important for the student to start to familiarize him or herself with these texts, primarily for the purpose of getting closer to the source.
Perhaps, as some have insisted, these techniques were not meant to be studied without the aid of a Guru. However, this belies the number of successful and accurate astrologers who are able to utilize Jyotish techniques successfully without a Jyotish Guru. This does not mean that I downgrade the importance of learning from those who have come before us, but I think that the Jyotir Vidya reveals itself to the sincere soul. Jyotish has rules, of that there is no doubt, but after the rules are learned, creativity can be introduced, and tested. I have seen quite a few eminent teachers disagree with each other. Every teacher has something of value to teach us. But keep in mind that the most important teacher is the Ishta Devata -- the teacher inside.