PoSe is by far the magnum opus. PaKa was written first and SiSa was written a dozen or so years later but historically SiSa happens about a decade or two before PaKa. PaKa is short (one-fifth the size of the other two). I liked the story of PaKa a lot. [although the movie version was totally butchered]. And just like how PoSe (which happens about 300 years after PaKa/SiSa) is all about Chozhas, the other two are about Pallavas. Very fascinating reads - will totally recommend it.
If you like Science and Music (in this case, western classical music), and biographies/history related to the science/music characters, then you will like my list a lot.
Please feel free to get in touch offline - can share more details. [I have the same id as the hn id in google/gmail as well].
PS: the goodreads link you posted takes me to my year_in_books page - can you please share your public url? Would love to see your reading list. thanks.