You can more or less find these books by going to Amazon and searching for Essbase, but I wanted to draw some attention to a few of the books out there:

Developing Essbase Applications: Advanced Techniques for Finance and IT Professionals

This a solid Essbase book written by many of my colleagues. I have reviewed it previously – check out Amazon for a more in-depth review.

Developing Essbase Applications: Hybrid Techniques and Practices

The second edition and followup to the previous book. Another essential book for the consummate Essbase professional.