I am looking for some texts that could teach the basics of Mantra Shastra. I am specially interested in their reasoning, pronunciation and historical context. Kindly recommend texts of the same kind.
To learn about Mantra Shastra, One can read Sri Vidyarnava Tantra. It deals with mantra and vidhya in great depth. The text also covers yantram for each mahavidya and explain in detail. I found Hindi version of the book in 2 parts.
Link to the books:
Garland of letters by by Arthur Avalon is another option which directly deals with Mantra only. The_Garland_of_Letters-_By_Arthur_Avalon