Personal advice for reading through the series, including non-required and extra-canonical material. There are some particularly hard-to-find fan translations when official material is not available, so here is a google drive link to a compilation fan efforts have put together that encompasses almost everything.
Additional short stories provided not here on MAL include:
"Rey Infinito - El Aleph" - short story published in 3 arcs, following Lisa Lisa between Parts 2 and 3
"The Anatomy Lesson of Dr. Nicolaes Tulp" - Short DRAFT scrapped that later became "The Book: Jojo's Bizarre Adventure 4th Another Day"
"No Love Like A Parent's", & "Testimione di gangster" - both Part 5 prequels focusing on La Squadra members
Same idea with "Risotto Nero Observes", which can be found fan-translated here: https://docs.google.com/document/d/1VJU-U6Kt-g76lufKH-J0jpX2YPDuXdi0Mok1AJ8F7dc/edit?usp=sharing
"Heaven's Door" - unrelated to Jojo Canon, but with heavy reference to Parts 4 & 8
Anything indicated as "available online' without cited sources or official translations are considered a fairly easy find on manga websites like MangaDex that I don't think people need my help to locate.
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