The Art of PostgreSQL is great and super thorough. Knowing the author I can't fault him on price for the effort he put into it. But also your point of students

The Art of PostgreSQL is great and super thorough. Knowing the author I can't fault him on price for the effort he put into it. But also your point of students and developers in low income countries completely understand that side. It's a shameless plug but we built our Postgres playground with tutorials on a number of topics which are completely free aiming to help target some of that audience - https://www.crunchydata.com/developers/tutorials https://www.crunchydata.com/developers/tutorials