I have to say I did my studies in German therefore I can not fully name all the English or US sources.

Even by an in depth study of the Peloponnesian war you should figure out first on what your focus lies. It helps you understand this complex and wide conflict with a lot of protagonists and city states and even empires involved.

Reading the primary source on a subject like in this case Thucydides is never wrong. Start there and continue with Xenophon's Hellenica I-II.3.10 because Thucydides died before he could finish his work and Xenophon was also associated to Sparta and give a view into their site of the way, which is missing in Thucycidedes reports. You could also look into Diodorus Book XI-XIII and in the plays of Aristophanes (for example The Knights).

I suggest you don't just read the primary sources, but also read about them. What were their biases? How did they work? What were their sources? How far away are they from the actual event?

After you read the primary sources you can start reading secondary sources.

You can read Kagans works, but also R. Meiggs "The Athenian Empire".You can also read J. Balcer "Seperatism and Anti-Separatism in the Athenian Empire".

Marc G. DeSantis has an interesting work about the Naval History of in the Peloponnesian war called "A Naval History of the Peloponnesian War: Ships, Men and Money in the War at Sea, 431-404 BC".

You can also read Paul Cartledges "The Spartans: An epic History" it can also can give you a little insight in the Spartan culture and society.

If you are interested in the "Plague of Athens" you can read up on Karl-Heinz Levens "Thkydides und die "Pest" in Athen" but I don't know if there is an English version of it. Hereby I would suggest more science papers like from Alan Shapiro "No proof that typhoid caused the Plague of Athens (a reply to Papagrigorakis et al.)" and "Insufficient phylogenetic analysis may not exclude candidacy of typhoid fever as a probable cause of the Plague of Athens (reply to Shapiro et al.)" and go from there. Medical historians and archaeologists of course still discus it.

I think this will take a while. Have fun studying it is an excellent an exciting topic, enjoy!