You can find recommended materials on the Qlik Sense Certification page: Qlik Sense Data Visualization Certification.
The script syntax and functions in Qlik Sense are almost identical to those of Qlikview. The modeling concepts haven't changed either. So you can also make use of the resources available for Qlikview to help prepare for this exam.
There are plenty of good books out there. Qlikview 11 for Developers and Qlikview Your Business are two of the best resources.