Previously I recommended five non-evaluation books that help me formulate foundational principles for transformative evaluation. Click link
There are two evaluation books that I consider most relevant for transformative evaluators that have a good understanding of the general principles of program evaluation.
Fourth Generation Evaluation, by Egon G. Guba and Yvonne S. Lincoln, is a comprehensive description of constructivist evaluation. This approach, which is an alternative to evaluation approaches that are based on a scientific epistemology, provides the framework for designing and implementing transformative evaluation.
Transformative Research and Evaluation, by Donna M. Mertens, describes evaluation as a means to promote human rights and social justice. This is an important component of transformative evaluation.
The attached file is a list of other evaluation references that are helpful to me. May they be helpful to you on your journey toward being a transformative evaluator. Click link: Eval Books 2015