Brazen academic fraud. Gurukkal is incapable of evaluating any kind of evidence, manages to be ignorant of basic terms and concepts in a way that would be embarrassing in a middle-schooler, and writes as if he doesn't believe words can have meaning. Rampant typos and grammatical errors confirm this book hasn't even seen a proofreader, much less the peer review the Oxford University Press assures readers all of its books go through. I suppose taking it apart for its contents would be beside the point, anyway: those contents are largely effectively automatic writing, and the only reason they aren't literally lorem ipsum is that Gurukkal wanted the book to look plausible to someone just flipping through it skimming section titles and looking at illustrations, not just standing on a shelf.
(Those illustrations, incidentally, are all labelled "Source: Author", presumably because someone told him he had to have a source for them; two of them appear to be scans of print-outs of low-res bitmaps of drawings of "Graeco-Roman" ships Gurukkal found somewhere—you can see the creases in the printer paper, but also the individual pixels in the drawings—that I don't doubt he physically handed to some poor editor, three are different crops of the same map, otherwise apparently unedited, and the final one is a map bizarrely labelled "not to scale", which I think is an admission that the lines added on by Gurukkal don't correspond to any kind of reality, because it's just a standard relief map of southern India otherwise.)
No conclusions are reached, nothing is synthesised; no rethinking—or indeed thinking—of any kind happens. That this garbage managed to get published by, again, the Oxford University Press is absolutely disgraceful, and the fact that Gurukkal apparently has a career as an academic—especially as a historian!—is an indictment of India's entire system of higher education.
(Someone at the OUP seems to have noticed eventually, because they're very reluctant to sell this book outside of India. I ordered it from their website, and it took over a year to get here; when it finally did, it had a price tag in rupees (₹1655, which is less than half the list price).)