I have to disagree with Nesacat here. If you read the Indian editions of the work, as I did, Banker clearly states that his intention was to use modern Indian English for his retelling, in the same way that other writers over the ages have used their own contemporary idioms for retelling. But I can see that some non-Indian (or non-resident Indian) readers might not appreciate the use of Indian English as opposed to more westernized usage. As for the colloquilisms, they are very much in keeping with the style of the work and are consistent throughout the series--I noticed even Urdu, Gujarati, Tamizh and other languages used freely. They are clearly meant to reflect the diversity and richness of Indian cultures.
Who was it who said, language is created by people in the real world, not in a laboratory.
I would strongly recommend reading Banker's Ramayana series. If nothing else, it is the first attempt on this scale to retell a great Indian tale for the present age. The older versions are wonderful and will always last. But if we cannot accept new works, especially ones as rich and inventive as these, then we might as well put up a tombstone and say a last prayer. A living language, a living culture, a living legend...that is the Ramayana.
One thing I do agree with is that it's necessary to read the traditional versions first, as Banker himself recommends strongly--he clearly states in his introduction and afterword that his retelling is not intended for those unfamiliar with the epic, or non-Indians. Only those intimately familiar with the epic will be able to truly relish this ultra-modern retelling.