We are hard at work on 4 books: Just completed
PostGIS In Action 3rd Edition (available now for purchase in LiveBook form directly from Manning and will be out Sept 15th 2021 in hard-copy),
pgRouting: A Practical Guide 2nd edition, a completely new book on PostgreSQL which we'll give more details of later,
and
SQL in a Nutshell (4th Edition) which covers ANSI-SQL:2016 and it's implementation in PostgreSQL, MariaDb, MySQL, Oracle, and SQL Server.
Explore in more detail the DBMS that make PostGIS and pgRouting so powerful with our latest book PostgreSQL: Up and Running 3rd Edition covers PostgreSQL 9.4-10 hard-copy and Kindle from Amazon and
EBook from O'Reilly.