looking for a lighter alternative to cognos express
I have deployed  Logi Reports at a client and the free version is just fine for the users where I am.  You can pay for the upgraded version which offers OLAP-like abilities. 2016 Update Logi no longer issues a free version. The paid version now has dashboard and analytic tools. 

This product was mentioned in another post iccube as a free OLAP but I have not used it.  It looks to me like it tries to emulate the built in features that Oracle has on a Java platform.

You don't mention the infrastructure or technical skills of the client.  These are important considerations.  A tool that is "too complicated" will only results in calls to you to dumb it down.

The features I recommend considering are:


how many brands of database can it connect to?  Does it work with the versions you have?
How easy is to configure access and permissions with the client's infrastructure? Active Directory is a standard for many places and should be an option.
How fast is the rendering engine or how much patience does your client have to wait for results?  (Of course database structure has a much bigger effect on performance than the reporting engine)
Do you want a product with wizards that make it easy to deploy reports?
Can you craft a query in SQL and then drop it into the report?  This is incredibly handy for testing and development.