I recently received an email from a friend and colleague from the United Kingdom. I have always found his work to be impeccable . . . and now I find it is also very affordable.
Here's the essence of the email:
Electronic Evidence (4th edition, Institute of Advanced Legal Studies for the SAS Humanities Digital Library, School of Advanced Study, University of London, 2017) http://ials.sas.ac.uk/digital/humanities-digital-library/observing-law-ials-open-book-service-law/electronic-evidence
Electronic Signatures in Law (4th edition, Institute of Advanced Legal Studies for the SAS Humanities Digital Library, School of Advanced Study, University of London, 2016) http://ials.sas.ac.uk/digital/humanities-digital-library/observing-law-ials-open-book-service-law/electronic-signatures
Digital Evidence and Electronic Signature Law Review http://journals.sas.ac.uk/deeslr/ (also available in the LexisNexis and HeinOnline electronic databases)