Prof. Subhash Kak has put his book The Astronomical Code of the Rig Veda in the public domain (via Michel Danino). From the introduction of the book
My own discovery was triggered by an essay in a popular magazine in November 1992 pointing out the marvelous coincidence that the moon and the sun are nearly of identical size when viewed from the earth. I had an overpowering feeling that the matter of size had something to do with the structure of the R. gveda. Checking the text in my library, I quickly discovered that the number of hymns encoded facts about the passage of the sun and the moon. The next task was to make sure that the correspondence was not just a coincidence, which required a careful sifting of numerical and textual data. I later found a confirmation of these numbers in the structure of the Atharvaveda and the Bhagavadgita.
There are those who argue that human progress can be measured only in terms of scientific progress. To such people the question of the science of the R. gveda is of much importance, for it is the oldest complete book that has come down to mankind.
Scholarly opinion has often swung between two extreme views on the past: one barbaric, the other idyllic. In truth, the past was much more of a complex affair than suggested by either of these labels. The discovery of the astronomical code not only allows us a new look at the rise of early science, it also focuses on the need to find the developmental process at the basis of the hymns[The Astronomical Code of the Rig Veda]
I have not read this book yet, but will do soon. You can download the entire PDF here