No select privileges when not connecting from login postgres

I'm trying to get a new build of 9.6.1 working on a machine
running Debian stable (jessie) and I'm seeing some odd
behavior where things work correctly if I run psql when
logged in as postgres, but if I run it as user 'doom' (my
usual login), I don't seem to have any select privileges.
Even this fails silenlty:

select 'world' as hello;

But if run logged in as postgres, all is well:

sudo su - postgres
/usr/local/pgsql/bin/psql --dbname=doom --username=doom
doom=# select 'world' as hello;
select 'world' as hello;
hello
-------
world
(1 row)

Note that I'm talking about the unix logins, in both cases
the postgresql username/role is 'doom' (which has Superuser
privileges and is the owner of the 'doom' database).

Looking at how the program files are installed, they're all
owned by 'root' with group 'staff':

ls -la /usr/local/pgsql/bin/psql
-rwxr-xr-x 1 root staff 516824 Nov 26 23:20 /usr/local/pgsql/bin/psql

So I added doom to the staff group and reloaded pg, but that
didn't help either. The files in the data tree are all
owned by postgres, but I don't think that's unusual:

drwx------ 1 postgres postgres 42 Nov 26 16:14 base

I'm running out of ideas for things to check. Any suggestions?