Center for Computer-Assisted Legal Instruction (CALI)

CALI is a non-profit consortium of law schools, law libraries, and related organizations. Schools and organizations within the consortium conduct applied research on computer-mediated legal education in order to develop tools to facilitate legal education and access to justice. There is an extensive list of free eBooks on various legal topics and lessons are available to CALI members 

Some eBook examples:

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Openly licensed but not OER - Look out for restrictions on modification and/or redistribution.The resources on CALI are openly licensed but not OER.