This is first book in Ram Chandra Series. Overall, I enjoyed reading it. Amish Tripathi picked Ramayana mythology as skeletal story to build his fantasy story. This is brilliant and risky approach, but so far, it has paid off well. Rama Chandra series is second highest selling series in Indian publishing history. It's brilliant because the story line is more or less set. It's risky because taking too much liberty with story line and using modern influence may not be received well by readers, especially those familiar with Ramayana story line.
Author treads this line carefully.
The good: Book explores side characters in Ramayana and builds stories around them (Mantara, Kaikeyi and reason for her two boons, Vashishta and Vishwamitra). This is great approach because these characters are have influential, although, brief presence in Ramayana story line. So, building on them will be non-controversial. Author kept the story line tight. It's a perfect page turner.
Can be better: Quality of writing. One of the praises on the cover goes like: "He's Tolkien of India". In terms of quality of writing (English), that comparison is so off. Reading the book felt like a friend speaking to me. It must be taken up few notches.