The premise is both interesting and valid. Hindu resistance to early Muslim invasions is not a subject that has received a lot of attention from our prominent historians. It is a fact that it took a few centuries for Islamic invaders to establish a permanent foothold, and eventually empire, in India and the subject deserves its due recognition; that is something this book seeks to remedy.
The book suffers from a few faults though. The first is the paucity of epigraphic evidence from Indian sources: we just weren’t good at recording history for posterity. Most of the information in here comes from Arab, and later, Persian authors and chroniclers. These data necessarily suffer from bias, cherry-picking, and lack of accuracy. The second is the author’s attempt to explain the reasons for the eventual failure of the Rajputs to keep the invaders at bay. This is where the book really gets off the rails and we are treated to harangues about loss of moral fabric (re: Khajuraho et al) and similar other tropes. The author’s claims that Indian society was a just, peaceful utopia before the invasions began do not ring true and tend to reveal his agendum behind it all.
Still, it is a book worth reading even with all the typos and spelling errors and what not; this is not information that is provided in mainstream texts, and most of it is not generally available or known. But someone proofread it, please!